diff --git a/includes/form.inc b/includes/form.inc
index c0163ca..c756b50 100644
--- a/includes/form.inc
+++ b/includes/form.inc
@@ -3639,14 +3639,7 @@ function theme_textfield($variables) {
   if ($element['#autocomplete_path'] && drupal_valid_path($element['#autocomplete_path'])) {
     drupal_add_library('system', 'drupal.autocomplete');
     $element['#attributes']['class'][] = 'form-autocomplete';
-
-    $attributes = array();
-    $attributes['type'] = 'hidden';
-    $attributes['id'] = $element['#attributes']['id'] . '-autocomplete';
-    $attributes['value'] = url($element['#autocomplete_path'], array('absolute' => TRUE));
-    $attributes['disabled'] = 'disabled';
-    $attributes['class'][] = 'autocomplete';
-    $extra = '<input' . drupal_attributes($attributes) . ' />';
+    $element['#attributes']['data-autocomplete-path'] = url($element['#autocomplete_path'], array('absolute' => TRUE));
   }
 
   $output = '<input' . drupal_attributes($element['#attributes']) . ' />';
diff --git a/misc/autocomplete.js b/misc/autocomplete.js
index 5e85be4..a7a51b7 100644
--- a/misc/autocomplete.js
+++ b/misc/autocomplete.js
@@ -5,317 +5,65 @@
  */
 Drupal.behaviors.autocomplete = {
   attach: function (context, settings) {
-    var acdb = [];
-    $('input.autocomplete', context).once('autocomplete', function () {
-      var uri = this.value;
-      if (!acdb[uri]) {
-        acdb[uri] = new Drupal.ACDB(uri);
-      }
-      var $input = $('#' + this.id.substr(0, this.id.length - 13))
-        .attr('autocomplete', 'OFF')
-        .attr('aria-autocomplete', 'list');
-      $($input[0].form).submit(Drupal.autocompleteSubmit);
-      $input.parent()
-        .attr('role', 'application')
-        .append($('<span class="element-invisible" aria-live="assertive"></span>')
-          .attr('id', $input.attr('id') + '-autocomplete-aria-live')
-        );
-      new Drupal.jsAC($input, acdb[uri]);
-    });
-  }
-};
-
-/**
- * Prevents the form from submitting if the suggestions popup is open
- * and closes the suggestions popup when doing so.
- */
-Drupal.autocompleteSubmit = function () {
-  return $('#autocomplete').each(function () {
-    this.owner.hidePopup();
-  }).size() == 0;
-};
-
-/**
- * An AutoComplete object.
- */
-Drupal.jsAC = function ($input, db) {
-  var ac = this;
-  this.input = $input[0];
-  this.ariaLive = $('#' + $input.attr('id') + '-autocomplete-aria-live');
-  this.db = db;
-
-  $input
-    .keydown(function (event) { return ac.onkeydown(this, event); })
-    .keyup(function (event) { ac.onkeyup(this, event); })
-    .blur(function () { ac.hidePopup(); ac.db.cancel(); });
-
-};
-
-/**
- * Handler for the "keydown" event.
- */
-Drupal.jsAC.prototype.onkeydown = function (input, e) {
-  if (!e) {
-    e = window.event;
-  }
-  switch (e.keyCode) {
-    case 40: // down arrow.
-      this.selectDown();
-      return false;
-    case 38: // up arrow.
-      this.selectUp();
-      return false;
-    default: // All other keys.
-      return true;
-  }
-};
-
-/**
- * Handler for the "keyup" event.
- */
-Drupal.jsAC.prototype.onkeyup = function (input, e) {
-  if (!e) {
-    e = window.event;
-  }
-  switch (e.keyCode) {
-    case 16: // Shift.
-    case 17: // Ctrl.
-    case 18: // Alt.
-    case 20: // Caps lock.
-    case 33: // Page up.
-    case 34: // Page down.
-    case 35: // End.
-    case 36: // Home.
-    case 37: // Left arrow.
-    case 38: // Up arrow.
-    case 39: // Right arrow.
-    case 40: // Down arrow.
-      return true;
-
-    case 9:  // Tab.
-    case 13: // Enter.
-    case 27: // Esc.
-      this.hidePopup(e.keyCode);
-      return true;
-
-    default: // All other keys.
-      if (input.value.length > 0)
-        this.populatePopup();
-      else
-        this.hidePopup(e.keyCode);
-      return true;
-  }
-};
-
-/**
- * Puts the currently highlighted suggestion into the autocomplete field.
- */
-Drupal.jsAC.prototype.select = function (node) {
-  this.input.value = $(node).data('autocompleteValue');
-};
-
-/**
- * Highlights the next suggestion.
- */
-Drupal.jsAC.prototype.selectDown = function () {
-  if (this.selected && this.selected.nextSibling) {
-    this.highlight(this.selected.nextSibling);
-  }
-  else if (this.popup) {
-    var lis = $('li', this.popup);
-    if (lis.size() > 0) {
-      this.highlight(lis.get(0));
-    }
-  }
-};
-
-/**
- * Highlights the previous suggestion.
- */
-Drupal.jsAC.prototype.selectUp = function () {
-  if (this.selected && this.selected.previousSibling) {
-    this.highlight(this.selected.previousSibling);
-  }
-};
-
-/**
- * Highlights a suggestion.
- */
-Drupal.jsAC.prototype.highlight = function (node) {
-  if (this.selected) {
-    $(this.selected).removeClass('selected');
-  }
-  $(node).addClass('selected');
-  this.selected = node;
-  $(this.ariaLive).html($(this.selected).html());
-};
-
-/**
- * Unhighlights a suggestion.
- */
-Drupal.jsAC.prototype.unhighlight = function (node) {
-  $(node).removeClass('selected');
-  this.selected = false;
-  $(this.ariaLive).empty();
-};
-
-/**
- * Hides the autocomplete suggestions.
- */
-Drupal.jsAC.prototype.hidePopup = function (keycode) {
-  // Select item if the right key or mousebutton was pressed.
-  if (this.selected && ((keycode && keycode != 46 && keycode != 8 && keycode != 27) || !keycode)) {
-    this.input.value = $(this.selected).data('autocompleteValue');
-  }
-  // Hide popup.
-  var popup = this.popup;
-  if (popup) {
-    this.popup = null;
-    $(popup).fadeOut('fast', function () { $(popup).remove(); });
-  }
-  this.selected = false;
-  $(this.ariaLive).empty();
-};
-
-/**
- * Positions the suggestions popup and starts a search.
- */
-Drupal.jsAC.prototype.populatePopup = function () {
-  var $input = $(this.input);
-  var position = $input.position();
-  // Show popup.
-  if (this.popup) {
-    $(this.popup).remove();
-  }
-  this.selected = false;
-  this.popup = $('<div id="autocomplete"></div>')[0];
-  this.popup.owner = this;
-  $(this.popup).css({
-    top: parseInt(position.top + this.input.offsetHeight, 10) + 'px',
-    left: parseInt(position.left, 10) + 'px',
-    width: $input.innerWidth() + 'px',
-    display: 'none'
-  });
-  $input.before(this.popup);
-
-  // Do search.
-  this.db.owner = this;
-  this.db.search(this.input.value);
-};
-
-/**
- * Fills the suggestion popup with any matches received.
- */
-Drupal.jsAC.prototype.found = function (matches) {
-  // If no value in the textfield, do not show the popup.
-  if (!this.input.value.length) {
-    return false;
-  }
-
-  // Prepare matches.
-  var ul = $('<ul></ul>');
-  var ac = this;
-  for (key in matches) {
-    $('<li></li>')
-      .html($('<div></div>').html(matches[key]))
-      .mousedown(function () { ac.select(this); })
-      .mouseover(function () { ac.highlight(this); })
-      .mouseout(function () { ac.unhighlight(this); })
-      .data('autocompleteValue', key)
-      .appendTo(ul);
-  }
-
-  // Show popup with matches, if any.
-  if (this.popup) {
-    if (ul.children().size()) {
-      $(this.popup).empty().append(ul).show();
-      $(this.ariaLive).html(Drupal.t('Autocomplete popup'));
-    }
-    else {
-      $(this.popup).css({ visibility: 'hidden' });
-      this.hidePopup();
-    }
-  }
-};
-
-Drupal.jsAC.prototype.setStatus = function (status) {
-  switch (status) {
-    case 'begin':
-      $(this.input).addClass('throbbing');
-      $(this.ariaLive).html(Drupal.t('Searching for matches...'));
-      break;
-    case 'cancel':
-    case 'error':
-    case 'found':
-      $(this.input).removeClass('throbbing');
-      break;
-  }
-};
-
-/**
- * An AutoComplete DataBase object.
- */
-Drupal.ACDB = function (uri) {
-  this.uri = uri;
-  this.delay = 300;
-  this.cache = {};
-};
-
-/**
- * Performs a cached and delayed search.
- */
-Drupal.ACDB.prototype.search = function (searchString) {
-  var db = this;
-  this.searchString = searchString;
-
-  // See if this string needs to be searched for anyway.
-  searchString = searchString.replace(/^\s+|\s+$/, '');
-  if (searchString.length <= 0 ||
-    searchString.charAt(searchString.length - 1) == ',') {
-    return;
-  }
-
-  // See if this key has been searched for before.
-  if (this.cache[searchString]) {
-    return this.owner.found(this.cache[searchString]);
-  }
-
-  // Initiate delayed search.
-  if (this.timer) {
-    clearTimeout(this.timer);
-  }
-  this.timer = setTimeout(function () {
-    db.owner.setStatus('begin');
-
-    // Ajax GET request for autocompletion.
-    $.ajax({
-      type: 'GET',
-      url: db.uri + '/' + encodeURIComponent(searchString),
-      dataType: 'json',
-      success: function (matches) {
-        if (typeof matches.status == 'undefined' || matches.status != 0) {
-          db.cache[searchString] = matches;
-          // Verify if these are still the matches the user wants to see.
-          if (db.searchString == searchString) {
-            db.owner.found(matches);
+    // Act on textfields with the "form-autocomplete" class.
+    $('input.form-autocomplete', context).once('autocomplete', function() {
+      // Use jQuery UI Autocomplete on the textfield.
+      $(this).autocomplete({
+        // The autcomplete source is provided by the data-autocomplete-path
+        // attribute within the element itself.
+        source: function(request, response) {
+          // Get the desired term and construct the autocomplete URL for it.
+          var term = Drupal.autocompleteextractLast(request.term);
+          var url = $(this.element).attr('data-autocomplete-path') + '/' + encodeURIComponent(term);
+          // Make the AJAX request.
+          $.getJSON(url, function(data) {
+            // Drupal returns an object array, but we need a string array.
+            var terms = new Array();
+            $.each(data, function(key, value) {
+              terms.push(value);
+            });
+            // Send the new string array of terms to the jQuery UI list.
+            response(terms);
+          });
+        },
+        search: function() {
+          // Only search if there has been more then two characters in there.
+          var term = Drupal.autocompleteextractLast(this.value);
+          if (term.length < 2) {
+            return false;
           }
-          db.owner.setStatus('found');
+        },
+        focus: function() {
+          // Prevent value inserted on focus.
+          return false;
+        },
+        // It will select the search term based on the last item in the list.
+        select: function(event, ui) {
+          var terms = Drupal.autocompletesplit(this.value);
+          // Remove the current input.
+          terms.pop();
+          // Add the selected item.
+          terms.push(ui.item.value);
+          this.value = terms.join(", ");
+          return false;
         }
-      },
-      error: function (xmlhttp) {
-        alert(Drupal.ajaxError(xmlhttp, db.uri));
+      });
+    });
+
+    // Pop up the autocomplete if tab was entered.
+    $(this).bind('keydown', function(event) {
+      if (event.keyCode === $.ui.keyCode.TAB && $(this).data("autocomplete").menu.active) {
+        event.preventDefault();
       }
     });
-  }, this.delay);
+  }
 };
 
-/**
- * Cancels the current autocomplete request.
- */
-Drupal.ACDB.prototype.cancel = function () {
-  if (this.owner) this.owner.setStatus('cancel');
-  if (this.timer) clearTimeout(this.timer);
-  this.searchString = '';
+Drupal.autocompletesplit = function(val) {
+  return val.split(/,\s*/);
+};
+Drupal.autocompleteextractLast = function(term) {
+  return Drupal.autocompletesplit(term).pop();
 };
 
 })(jQuery);
diff --git a/modules/system/system.base-rtl.css b/modules/system/system.base-rtl.css
index 9099c9d..5ea42ed 100644
--- a/modules/system/system.base-rtl.css
+++ b/modules/system/system.base-rtl.css
@@ -4,14 +4,11 @@
  * Generic theme-independent base styles.
  */
 
-/**
- * Autocomplete.
- */
 /* Animated throbber */
 html.js input.form-autocomplete {
   background-position: 0% 2px;
 }
-html.js input.throbbing {
+html.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 0% -18px;
 }
 
diff --git a/modules/system/system.base.css b/modules/system/system.base.css
index a6748de..d6127e5 100644
--- a/modules/system/system.base.css
+++ b/modules/system/system.base.css
@@ -4,37 +4,13 @@
  * Generic theme-independent base styles.
  */
 
-/**
- * Autocomplete.
- *
- * @see autocomplete.js
- */
-/* Suggestion list */
-#autocomplete {
-  border: 1px solid;
-  overflow: hidden;
-  position: absolute;
-  z-index: 100;
-}
-#autocomplete ul {
-  list-style: none;
-  list-style-image: none;
-  margin: 0;
-  padding: 0;
-}
-#autocomplete li {
-  background: #fff;
-  color: #000;
-  cursor: default;
-  white-space: pre;
-}
 /* Animated throbber */
 html.js input.form-autocomplete {
   background-image: url(../../misc/throbber.gif);
   background-position: 100% 2px; /* LTR */
   background-repeat: no-repeat;
 }
-html.js input.throbbing {
+html.js input.form-autocomplete.ui-autocomplete-loading {
   background-position: 100% -18px; /* LTR */
 }
 
diff --git a/modules/system/system.module b/modules/system/system.module
index 21b23f4..309f3ed 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -1159,6 +1159,9 @@ function system_library() {
     'js' => array(
       'misc/autocomplete.js' => array('group' => JS_DEFAULT),
     ),
+    'dependencies' => array(
+      array('system', 'ui.autocomplete'),
+    ),
   );
 
   // jQuery.
diff --git a/themes/bartik/css/style.css b/themes/bartik/css/style.css
index 75e43b0..72a3bfa 100644
--- a/themes/bartik/css/style.css
+++ b/themes/bartik/css/style.css
@@ -1330,9 +1330,6 @@ input.form-button-disabled:active,
 }
 
 /* Animated throbber */
-html.js input.form-autocomplete {
-  background-position: 100% 4px; /* LTR */
-}
 html.js input.throbbing {
   background-position: 100% -16px; /* LTR */
 }
diff --git a/themes/garland/style.css b/themes/garland/style.css
index f36fa96..55b9181 100644
--- a/themes/garland/style.css
+++ b/themes/garland/style.css
@@ -927,15 +927,6 @@ tr.even td.menu-disabled {
 }
 
 /**
- * Autocomplete.
- */
-#autocomplete li {
-  cursor: default;
-  padding: 2px;
-  margin: 0;
-}
-
-/**
  * Collapsible fieldsets
  */
 fieldset {
@@ -1137,7 +1128,6 @@ table.system-status-report th {
   border-color: #d3e7f4;
 }
 
-#autocomplete li.selected,
 tr.selected td,
 tr.selected td.active {
   background: #027ac6;
diff --git a/themes/seven/style.css b/themes/seven/style.css
index 66303c5..00a3ed9 100644
--- a/themes/seven/style.css
+++ b/themes/seven/style.css
@@ -594,7 +594,6 @@ div.teaser-checkbox .form-item,
 .form-item label.option input {
   vertical-align: middle;
 }
-.form-disabled input.form-autocomplete,
 .form-disabled input.form-text,
 .form-disabled input.form-file,
 .form-disabled textarea.form-textarea,
@@ -681,7 +680,6 @@ input.form-button-disabled:active {
   text-shadow: none;
   color: #999;
 }
-input.form-autocomplete,
 input.form-text,
 input.form-file,
 textarea.form-textarea,
@@ -699,9 +697,6 @@ select.form-select:focus {
   color: #000;
   border-color: #ace;
 }
-html.js input.form-autocomplete {
-  background-position: 100% 4px;
-}
 html.js input.throbbing {
   background-position: 100% -16px;
 }