diff --git a/src/TabComplete.js b/src/TabComplete.js
new file mode 100644
index 0000000000..b84192e418
--- /dev/null
+++ b/src/TabComplete.js
@@ -0,0 +1,300 @@
+/*
+Copyright 2015 OpenMarket Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+var Entry = require("./TabCompleteEntries").Entry;
+
+const DELAY_TIME_MS = 1000;
+const KEY_TAB = 9;
+const KEY_SHIFT = 16;
+const KEY_WINDOWS = 91;
+
+// NB: DO NOT USE \b its "words" are roman alphabet only!
+//
+// Capturing group containing the start
+// of line or a whitespace char
+//     \_______________       __________Capturing group of 1 or more non-whitespace chars
+//                    _|__  _|_         followed by the end of line
+//                   /    \/   \
+const MATCH_REGEX = /(^|\s)(\S+)$/;
+
+class TabComplete {
+
+    constructor(opts) {
+        opts.startingWordSuffix = opts.startingWordSuffix || "";
+        opts.wordSuffix = opts.wordSuffix || "";
+        opts.allowLooping = opts.allowLooping || false;
+        opts.autoEnterTabComplete = opts.autoEnterTabComplete || false;
+        opts.onClickCompletes = opts.onClickCompletes || false;
+        this.opts = opts;
+        this.completing = false;
+        this.list = []; // full set of tab-completable things
+        this.matchedList = []; // subset of completable things to loop over
+        this.currentIndex = 0; // index in matchedList currently
+        this.originalText = null; // original input text when tab was first hit
+        this.textArea = opts.textArea; // DOMElement
+        this.isFirstWord = false; // true if you tab-complete on the first word
+        this.enterTabCompleteTimerId = null;
+        this.inPassiveMode = false;
+    }
+
+    /**
+     * @param {Entry[]} completeList
+     */
+    setCompletionList(completeList) {
+        this.list = completeList;
+        if (this.opts.onClickCompletes) {
+            // assign onClick listeners for each entry to complete the text
+            this.list.forEach((l) => {
+                l.onClick = () => {
+                    this.completeTo(l.getText());
+                }
+            });
+        }
+    }
+
+    /**
+     * @param {DOMElement}
+     */
+    setTextArea(textArea) {
+        this.textArea = textArea;
+    }
+
+    /**
+     * @return {Boolean}
+     */
+    isTabCompleting() {
+        // actually have things to tab over
+        return this.completing && this.matchedList.length > 1;
+    }
+
+    stopTabCompleting() {
+        this.completing = false;
+        this.currentIndex = 0;
+        this._notifyStateChange();
+    }
+
+    startTabCompleting() {
+        this.completing = true;
+        this.currentIndex = 0;
+        this._calculateCompletions();
+    }
+
+    /**
+     * Do an auto-complete with the given word. This terminates the tab-complete.
+     * @param {string} someVal
+     */
+    completeTo(someVal) {
+        this.textArea.value = this._replaceWith(someVal, true);
+        this.stopTabCompleting();
+        // keep focus on the text area
+        this.textArea.focus();
+    }
+
+    /**
+     * @param {Number} numAheadToPeek Return *up to* this many elements.
+     * @return {Entry[]}
+     */
+    peek(numAheadToPeek) {
+        if (this.matchedList.length === 0) {
+            return [];
+        }
+        var peekList = [];
+
+        // return the current match item and then one with an index higher, and
+        // so on until we've reached the requested limit. If we hit the end of
+        // the list of options we're done.
+        for (var i = 0; i < numAheadToPeek; i++) {
+            var nextIndex;
+            if (this.opts.allowLooping) {
+                nextIndex = (this.currentIndex + i) % this.matchedList.length;
+            }
+            else {
+                nextIndex = this.currentIndex + i;
+                if (nextIndex === this.matchedList.length) {
+                    break;
+                }
+            }
+            peekList.push(this.matchedList[nextIndex]);
+        }
+        // console.log("Peek list(%s): %s", numAheadToPeek, JSON.stringify(peekList));
+        return peekList;
+    }
+
+    handleTabPress(passive, shiftKey) {
+        var wasInPassiveMode = this.inPassiveMode && !passive;
+        this.inPassiveMode = passive;
+
+        if (!this.completing) {
+            this.startTabCompleting();
+        }
+
+        if (shiftKey) {
+            this.nextMatchedEntry(-1);
+        }
+        else {
+            // if we were in passive mode we got out of sync by incrementing the
+            // index to show the peek view but not set the text area. Therefore,
+            // we want to set the *current* index rather than the *next* index.
+            this.nextMatchedEntry(wasInPassiveMode ? 0 : 1);
+        }
+        this._notifyStateChange();
+    }
+
+    /**
+     * @param {DOMEvent} e
+     */
+    onKeyDown(ev) {
+        if (!this.textArea) {
+            console.error("onKeyDown called before a <textarea> was set!");
+            return;
+        }
+
+        if (ev.keyCode !== KEY_TAB) {
+            // pressing any key (except shift, windows, cmd (OSX) and ctrl/alt combinations)
+            // aborts the current tab completion
+            if (this.completing && ev.keyCode !== KEY_SHIFT &&
+                    !ev.metaKey && !ev.ctrlKey && !ev.altKey && ev.keyCode !== KEY_WINDOWS) {
+                // they're resuming typing; reset tab complete state vars.
+                this.stopTabCompleting();
+            }
+
+            // pressing any key at all (except tab) restarts the automatic tab-complete timer
+            if (this.opts.autoEnterTabComplete) {
+                clearTimeout(this.enterTabCompleteTimerId);
+                this.enterTabCompleteTimerId = setTimeout(() => {
+                    if (!this.completing) {
+                        this.handleTabPress(true, false);
+                    }
+                }, DELAY_TIME_MS);
+            }
+
+            return;
+        }
+
+        // tab key has been pressed at this point
+        this.handleTabPress(false, ev.shiftKey)
+
+        // prevent the default TAB operation (typically focus shifting)
+        ev.preventDefault();
+    }
+
+    /**
+     * Set the textarea to the next value in the matched list.
+     * @param {Number} offset Offset to apply *before* setting the next value.
+     */
+    nextMatchedEntry(offset) {
+        if (this.matchedList.length === 0) {
+            return;
+        }
+
+        // work out the new index, wrapping if necessary.
+        this.currentIndex += offset;
+        if (this.currentIndex >= this.matchedList.length) {
+            this.currentIndex = 0;
+        }
+        else if (this.currentIndex < 0) {
+            this.currentIndex = this.matchedList.length - 1;
+        }
+        var isTransitioningToOriginalText = (
+            // impossible to transition if they've never hit tab
+            !this.inPassiveMode && this.currentIndex === 0
+        );
+
+        if (!this.inPassiveMode) {
+            // set textarea to this new value
+            this.textArea.value = this._replaceWith(
+                this.matchedList[this.currentIndex].text,
+                this.currentIndex !== 0 // don't suffix the original text!
+            );
+        }
+
+        // visual display to the user that we looped - TODO: This should be configurable
+        if (isTransitioningToOriginalText) {
+            this.textArea.style["background-color"] = "#faa";
+            setTimeout(() => { // yay for lexical 'this'!
+                 this.textArea.style["background-color"] = "";
+            }, 150);
+
+            if (!this.opts.allowLooping) {
+                this.stopTabCompleting();
+            }
+        }
+        else {
+            this.textArea.style["background-color"] = ""; // cancel blinks TODO: required?
+        }
+    }
+
+    _replaceWith(newVal, includeSuffix) {
+        // The regex to replace the input matches a character of whitespace AND
+        // the partial word. If we just use string.replace() with the regex it will
+        // replace the partial word AND the character of whitespace. We want to
+        // preserve whatever that character is (\n, \t, etc) so find out what it is now.
+        var boundaryChar;
+        var res = MATCH_REGEX.exec(this.originalText);
+        if (res) {
+            boundaryChar = res[1]; // the first captured group
+        }
+        if (boundaryChar === undefined) {
+            console.warn("Failed to find boundary char on text: '%s'", this.originalText);
+            boundaryChar = "";
+        }
+
+        var replacementText = (
+            boundaryChar + newVal + (
+                includeSuffix ?
+                    (this.isFirstWord ? this.opts.startingWordSuffix : this.opts.wordSuffix) :
+                    ""
+            )
+        );
+        return this.originalText.replace(MATCH_REGEX, function() {
+            return replacementText; // function form to avoid `$` special-casing
+        });
+    }
+
+    _calculateCompletions() {
+        this.originalText = this.textArea.value; // cache starting text
+
+        // grab the partial word from the text which we'll be tab-completing
+        var res = MATCH_REGEX.exec(this.originalText);
+        if (!res) {
+            this.matchedList = [];
+            return;
+        }
+        // ES6 destructuring; ignore first element (the complete match)
+        var [ , boundaryGroup, partialGroup] = res;
+        this.isFirstWord = partialGroup.length === this.originalText.length;
+
+        this.matchedList = [
+            new Entry(partialGroup) // first entry is always the original partial
+        ];
+
+        // find matching entries in the set of entries given to us
+        this.list.forEach((entry) => {
+            if (entry.text.toLowerCase().indexOf(partialGroup.toLowerCase()) === 0) {
+                this.matchedList.push(entry);
+            }
+        });
+
+        // console.log("_calculateCompletions => %s", JSON.stringify(this.matchedList));
+    }
+
+    _notifyStateChange() {
+        if (this.opts.onStateChange) {
+            this.opts.onStateChange(this.completing);
+        }
+    }
+};
+
+module.exports = TabComplete;
diff --git a/src/TabCompleteEntries.js b/src/TabCompleteEntries.js
new file mode 100644
index 0000000000..6d1a51c9b2
--- /dev/null
+++ b/src/TabCompleteEntries.js
@@ -0,0 +1,101 @@
+/*
+Copyright 2015 OpenMarket Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+var React = require("react");
+var sdk = require("./index");
+
+class Entry {
+    constructor(text) {
+        this.text = text;
+    }
+
+    /**
+     * @return {string} The text to display in this entry.
+     */
+    getText() {
+        return this.text;
+    }
+
+    /**
+     * @return {ReactClass} Raw JSX
+     */
+    getImageJsx() {
+        return null;
+    }
+
+    /**
+     * @return {?string} The unique key= prop for React dedupe
+     */
+    getKey() {
+        return null;
+    }
+
+    /**
+     * Called when this entry is clicked.
+     */
+    onClick() {
+        // NOP
+    }
+}
+
+class MemberEntry extends Entry {
+    constructor(member) {
+        super(member.name || member.userId);
+        this.member = member;
+    }
+
+    getImageJsx() {
+        var MemberAvatar = sdk.getComponent("views.avatars.MemberAvatar");
+        return (
+            <MemberAvatar member={this.member} width={24} height={24} />
+        );
+    }
+
+    getKey() {
+        return this.member.userId;
+    }
+}
+
+MemberEntry.fromMemberList = function(members) {
+    return members.sort(function(a, b) {
+        var userA = a.user;
+        var userB = b.user;
+        if (userA && !userB) {
+            return -1; // a comes first
+        }
+        else if (!userA && userB) {
+            return 1; // b comes first
+        }
+        else if (!userA && !userB) {
+            return 0; // don't care
+        }
+        else { // both User objects exist
+            if (userA.lastActiveAgo < userB.lastActiveAgo) {
+                return -1; // a comes first
+            }
+            else if (userA.lastActiveAgo > userB.lastActiveAgo) {
+                return 1; // b comes first
+            }
+            else {
+                return 0; // same last active ago
+            }
+        }
+    }).map(function(m) {
+        return new MemberEntry(m);
+    });
+}
+
+module.exports.Entry = Entry;
+module.exports.MemberEntry = MemberEntry;
diff --git a/src/component-index.js b/src/component-index.js
index e7a74e0351..f10549ce4d 100644
--- a/src/component-index.js
+++ b/src/component-index.js
@@ -66,6 +66,7 @@ module.exports.components['views.rooms.RoomHeader'] = require('./components/view
 module.exports.components['views.rooms.RoomList'] = require('./components/views/rooms/RoomList');
 module.exports.components['views.rooms.RoomSettings'] = require('./components/views/rooms/RoomSettings');
 module.exports.components['views.rooms.RoomTile'] = require('./components/views/rooms/RoomTile');
+module.exports.components['views.rooms.TabCompleteBar'] = require('./components/views/rooms/TabCompleteBar');
 module.exports.components['views.settings.ChangeAvatar'] = require('./components/views/settings/ChangeAvatar');
 module.exports.components['views.settings.ChangeDisplayName'] = require('./components/views/settings/ChangeDisplayName');
 module.exports.components['views.settings.ChangePassword'] = require('./components/views/settings/ChangePassword');
diff --git a/src/components/structures/RoomView.js b/src/components/structures/RoomView.js
index 29e2d3d4ff..127fe2fdb8 100644
--- a/src/components/structures/RoomView.js
+++ b/src/components/structures/RoomView.js
@@ -33,6 +33,8 @@ var WhoIsTyping = require("../../WhoIsTyping");
 var Modal = require("../../Modal");
 var sdk = require('../../index');
 var CallHandler = require('../../CallHandler');
+var TabComplete = require("../../TabComplete");
+var MemberEntry = require("../../TabCompleteEntries").MemberEntry;
 var Resend = require("../../Resend");
 var dis = require("../../dispatcher");
 
@@ -76,6 +78,18 @@ module.exports = React.createClass({
         MatrixClientPeg.get().on("RoomMember.typing", this.onRoomMemberTyping);
         MatrixClientPeg.get().on("RoomState.members", this.onRoomStateMember);
         MatrixClientPeg.get().on("sync", this.onSyncStateChange);
+        // xchat-style tab complete, add a colon if tab
+        // completing at the start of the text
+        this.tabComplete = new TabComplete({
+            startingWordSuffix: ": ",
+            wordSuffix: " ",
+            allowLooping: false,
+            autoEnterTabComplete: true,
+            onClickCompletes: true,
+            onStateChange: (isCompleting) => {
+                this.forceUpdate();
+            }
+        });
     },
 
     componentWillUnmount: function() {
@@ -225,6 +239,11 @@ module.exports = React.createClass({
     },
 
     onRoomStateMember: function(ev, state, member) {
+        if (member.roomId === this.props.roomId) {
+            // a member state changed in this room, refresh the tab complete list
+            this._updateTabCompleteList(this.state.room);
+        }
+
         if (!this.props.ConferenceHandler) {
             return;
         }
@@ -287,6 +306,17 @@ module.exports = React.createClass({
 
         window.addEventListener('resize', this.onResize);
         this.onResize();
+
+        this._updateTabCompleteList(this.state.room);
+    },
+
+    _updateTabCompleteList: function(room) {
+        if (!room || !this.tabComplete) {
+            return;
+        }
+        this.tabComplete.setCompletionList(
+            MemberEntry.fromMemberList(room.getJoinedMembers())
+        );
     },
 
     _initialiseMessagePanel: function() {
@@ -1154,6 +1184,21 @@ module.exports = React.createClass({
                         </div>
                     );
                 }
+                else if (this.tabComplete.isTabCompleting()) {
+                    var TabCompleteBar = sdk.getComponent('rooms.TabCompleteBar');
+                    statusBar = (
+                        <div className="mx_RoomView_tabCompleteBar">
+                            <div className="mx_RoomView_tabCompleteImage">...</div>
+                            <div className="mx_RoomView_tabCompleteWrapper">
+                                <TabCompleteBar entries={this.tabComplete.peek(6)} />
+                                <div className="mx_RoomView_tabCompleteEol">
+                                    <img src="img/eol.svg" width="22" height="16" alt="->|"/>
+                                    Auto-complete
+                                </div>
+                            </div>
+                        </div>
+                    );
+                }
                 else if (this.state.hasUnsentMessages) {
                     statusBar = (
                         <div className="mx_RoomView_connectionLostBar">
@@ -1234,7 +1279,9 @@ module.exports = React.createClass({
             );
             if (canSpeak) {
                 messageComposer =
-                    <MessageComposer room={this.state.room} roomView={this} uploadFile={this.uploadFile} callState={this.state.callState} />
+                    <MessageComposer
+                        room={this.state.room} roomView={this} uploadFile={this.uploadFile}
+                        callState={this.state.callState} tabComplete={this.tabComplete} />
             }
 
             // TODO: Why aren't we storing the term/scope/count in this format
diff --git a/src/components/views/rooms/MessageComposer.js b/src/components/views/rooms/MessageComposer.js
index 67fb37d530..5ac4a24908 100644
--- a/src/components/views/rooms/MessageComposer.js
+++ b/src/components/views/rooms/MessageComposer.js
@@ -31,6 +31,7 @@ var MatrixClientPeg = require("../../../MatrixClientPeg");
 var SlashCommands = require("../../../SlashCommands");
 var Modal = require("../../../Modal");
 var CallHandler = require('../../../CallHandler');
+var MemberEntry = require("../../../TabCompleteEntries").MemberEntry;
 var sdk = require('../../../index');
 
 var dis = require("../../../dispatcher");
@@ -64,14 +65,13 @@ function mdownToHtml(mdown) {
 module.exports = React.createClass({
     displayName: 'MessageComposer',
 
+    propTypes: {
+        tabComplete: React.PropTypes.any
+    },
+
     componentWillMount: function() {
         this.oldScrollHeight = 0;
         this.markdownEnabled = MARKDOWN_ENABLED;
-        this.tabStruct = {
-            completing: false,
-            original: null,
-            index: 0
-        };
         var self = this;
         this.sentHistory = {
             // The list of typed messages. Index 0 is more recent
@@ -172,6 +172,9 @@ module.exports = React.createClass({
             this.props.room.roomId
         );
         this.resizeInput();
+        if (this.props.tabComplete) {
+            this.props.tabComplete.setTextArea(this.refs.textarea);
+        }
     },
 
     componentWillUnmount: function() {
@@ -197,13 +200,6 @@ module.exports = React.createClass({
             this.sentHistory.push(input);
             this.onEnter(ev);
         }
-        else if (ev.keyCode === KeyCode.TAB) {
-            var members = [];
-            if (this.props.room) {
-                members = this.props.room.getJoinedMembers();
-            }
-            this.onTab(ev, members);
-        }
         else if (ev.keyCode === KeyCode.UP) {
             var input = this.refs.textarea.value;
             var offset = this.refs.textarea.selectionStart || 0;
@@ -222,10 +218,9 @@ module.exports = React.createClass({
                 this.resizeInput();
             }
         }
-        else if (ev.keyCode !== KeyCode.SHIFT && this.tabStruct.completing) {
-            // they're resuming typing; reset tab complete state vars.
-            this.tabStruct.completing = false;
-            this.tabStruct.index = 0;
+
+        if (this.props.tabComplete) {
+            this.props.tabComplete.onKeyDown(ev);
         }
 
         var self = this;
@@ -349,104 +344,6 @@ module.exports = React.createClass({
         ev.preventDefault();
     },
 
-    onTab: function(ev, sortedMembers) {
-        var textArea = this.refs.textarea;
-        if (!this.tabStruct.completing) {
-            this.tabStruct.completing = true;
-            this.tabStruct.index = 0;
-            // cache starting text
-            this.tabStruct.original = textArea.value;
-        }
-
-        // loop in the right direction
-        if (ev.shiftKey) {
-            this.tabStruct.index --;
-            if (this.tabStruct.index < 0) {
-                // wrap to the last search match, and fix up to a real index
-                // value after we've matched.
-                this.tabStruct.index = Number.MAX_VALUE;
-            }
-        }
-        else {
-            this.tabStruct.index++;
-        }
-
-        var searchIndex = 0;
-        var targetIndex = this.tabStruct.index;
-        var text = this.tabStruct.original;
-
-        var search = /@?([a-zA-Z0-9_\-:\.]+)$/.exec(text);
-        // console.log("Searched in '%s' - got %s", text, search);
-        if (targetIndex === 0) { // 0 is always the original text
-            textArea.value = text;
-        }
-        else if (search && search[1]) {
-            // console.log("search found: " + search+" from "+text);
-            var expansion;
-
-            // FIXME: could do better than linear search here
-            for (var i=0; i<sortedMembers.length; i++) {
-                var member = sortedMembers[i];
-                if (member.name && searchIndex < targetIndex) {
-                    if (member.name.toLowerCase().indexOf(search[1].toLowerCase()) === 0) {
-                        expansion = member.name;
-                        searchIndex++;
-                    }
-                }
-            }
-
-            if (searchIndex < targetIndex) { // then search raw mxids
-                for (var i=0; i<sortedMembers.length; i++) {
-                    if (searchIndex >= targetIndex) {
-                        break;
-                    }
-                    var userId = sortedMembers[i].userId;
-                    // === 1 because mxids are @username
-                    if (userId.toLowerCase().indexOf(search[1].toLowerCase()) === 1) {
-                        expansion = userId;
-                        searchIndex++;
-                    }
-                }
-            }
-
-            if (searchIndex === targetIndex ||
-                    targetIndex === Number.MAX_VALUE) {
-                // xchat-style tab complete, add a colon if tab
-                // completing at the start of the text
-                if (search[0].length === text.length) {
-                    expansion += ": ";
-                }
-                else {
-                    expansion += " ";
-                }
-                textArea.value = text.replace(
-                    /@?([a-zA-Z0-9_\-:\.]+)$/, expansion
-                );
-                // cancel blink
-                textArea.style["background-color"] = "";
-                if (targetIndex === Number.MAX_VALUE) {
-                    // wrap the index around to the last index found
-                    this.tabStruct.index = searchIndex;
-                    targetIndex = searchIndex;
-                }
-            }
-            else {
-                // console.log("wrapped!");
-                textArea.style["background-color"] = "#faa";
-                setTimeout(function() {
-                     textArea.style["background-color"] = "";
-                }, 150);
-                textArea.value = text;
-                this.tabStruct.index = 0;
-            }
-        }
-        else {
-            this.tabStruct.index = 0;
-        }
-        // prevent the default TAB operation (typically focus shifting)
-        ev.preventDefault();
-    },
-
     onTypingActivity: function() {
         this.isTyping = true;
         if (!this.userTypingTimer) {
diff --git a/src/components/views/rooms/TabCompleteBar.js b/src/components/views/rooms/TabCompleteBar.js
new file mode 100644
index 0000000000..9668c4b3ac
--- /dev/null
+++ b/src/components/views/rooms/TabCompleteBar.js
@@ -0,0 +1,46 @@
+/*
+Copyright 2015 OpenMarket Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+'use strict';
+
+var React = require('react');
+var MatrixClientPeg = require("../../../MatrixClientPeg");
+
+module.exports = React.createClass({
+    displayName: 'TabCompleteBar',
+
+    propTypes: {
+        entries: React.PropTypes.array.isRequired
+    },
+
+    render: function() {
+        return (
+            <div className="mx_TabCompleteBar">
+            {this.props.entries.map(function(entry, i) {
+                return (
+                    <div key={entry.getKey() || i + ""} className="mx_TabCompleteBar_item"
+                            onClick={entry.onClick.bind(entry)} >
+                        {entry.getImageJsx()}
+                        <span className="mx_TabCompleteBar_text">
+                            {entry.getText()}
+                        </span>
+                    </div>
+                );
+            })}
+            </div>
+        );
+    }
+});