diff -u b/misc/autocomplete.js b/misc/autocomplete.js
--- b/misc/autocomplete.js
+++ b/misc/autocomplete.js
@@ -287,7 +287,8 @@
   this.timer = setTimeout(function () {
     db.owner.setStatus('begin');
 
-    // Ajax GET request for autocompletion.
+    // Ajax GET request for autocompletion. We use Drupal.encodePath instead of
+    // encodeURIComponent to allow autocomplete search terms to contain slashes.
     $.ajax({
       type: 'GET',
       url: db.uri + '/' + Drupal.encodePath(searchString),
diff -u b/modules/taxonomy/taxonomy.module b/modules/taxonomy/taxonomy.module
--- b/modules/taxonomy/taxonomy.module
+++ b/modules/taxonomy/taxonomy.module
@@ -312,6 +312,7 @@
     'type' => MENU_CALLBACK,
     'file' => 'taxonomy.pages.inc',
   );
+  // We append /%menu_tail so the search text may contain slashes.
   $items['taxonomy/autocomplete/%/%menu_tail'] = array(
     'title' => 'Autocomplete taxonomy',
     'page callback' => 'taxonomy_autocomplete',
@@ -322,9 +323,10 @@
     // Needed for menu_tail_load().
     'load arguments' => array('%map', '%index'),
   );
-  // This is needed because the autocomplete system relies on this path existing.
-  // See: http://drupal.org/node/93854
-  $items['taxonomy/autocomplete'] = array(
+  // This matches the vocabulary name without any search text. Even though this
+  // path is never called, its existence is checked by theme_textfield() and
+  // tested in ProfileTestAutocomplete.
+  $items['taxonomy/autocomplete/%'] = array(
     'title' => 'Autocomplete taxonomy',
     'page callback' => 'taxonomy_autocomplete',
     'access arguments' => array('access content'),
diff -u b/modules/taxonomy/taxonomy.test b/modules/taxonomy/taxonomy.test
--- b/modules/taxonomy/taxonomy.test
+++ b/modules/taxonomy/taxonomy.test
@@ -641,24 +641,38 @@
   }
 
   /**
-   * Test term autocompletion edge cases.
+   * Test term autocompletion edge cases with slashes in the names.
    */
   function testTermAutocompletion() {
-    $base = $this->randomName(2);
     // Add a term with a slash in the name.
-    $term = $this->createTerm($this->vocabulary);
-    $term->name = $base . '/' . $this->randomName();
-    taxonomy_term_save($term);
-    // Add a term with a slash in the name.
-    $term = $this->createTerm($this->vocabulary);
-    $term->name = $base . '/' . $this->randomName();
-    taxonomy_term_save($term);
+    $first_term = $this->createTerm($this->vocabulary);
+    $first_term->name = '10/16/2011';
+    taxonomy_term_save($first_term);
+    // Add another term that differs after the slash character.
+    $second_term = $this->createTerm($this->vocabulary);
+    $second_term->name = '10/17/2011';
+    taxonomy_term_save($second_term);
+
+    // Try to autocomplete a term name that matches both terms.
+    // We should get both term in a json encoded string.
+    $input = '10/';
+    $path = 'taxonomy/autocomplete/taxonomy_';
+    $path .= $this->vocabulary->machine_name . '/' . $input;
+    // The result order is not guaranteed, so check each term separately.
+    $url = url($path, array('absolute' => TRUE));
+    $result = drupal_http_request($url);
+    $data = drupal_json_decode($result->data);
+    $this->assertEqual($data[$first_term->name], check_plain($first_term->name), t('Autocomplete returned the first matching term'));
+    $this->assertEqual($data[$second_term->name], check_plain($second_term->name), t('Autocomplete returned the second matching term'));
 
-    // Try to autocomplete the term name, that contains a slash.
-    // We should only get a single term returned.
-    $input = substr($term->name, 0, 5);
-    $this->drupalGet('taxonomy/autocomplete/taxonomy_' . $this->vocabulary->machine_name . '/' . $input);
-    $this->assertRaw(drupal_json_encode(array($term->name => check_plain($term->name))), t('Autocomplete returns term %term_name after typing the first 4 letters, including a slash in the name.', array('%term_name' => $term->name)));
+    // Try to autocomplete a term name that matches 1st term.
+    // We should only get the first term in a json encoded string.
+    $input = '10/16';
+    $url = 'taxonomy/autocomplete/taxonomy_';
+    $url .= $this->vocabulary->machine_name . '/' . $input;
+    $this->drupalGet($url);
+    $target = array($first_term->name => check_plain($first_term->name));
+    $this->assertRaw(drupal_json_encode($target), t('Autocomplete returns only the expected matching term.'));
   }
 
   /**