--- includes/theme.inc	2008-08-02 21:01:02.000000000 +0200
+++ includes/theme.inc	2008-08-14 00:18:23.000000000 +0200
@@ -1509,11 +1509,14 @@
       if (count($children) > 0) {
         $data .= theme_item_list($children, NULL, $type, $attributes); // Render nested list
       }
+      
+      $zebra = ($i & 1) ? 'even' : 'odd';
+      $attributes['class'] = empty($attributes['class']) ? $zebra : $attributes['class'] . ' ' . $zebra;
       if ($i == 0) {
-        $attributes['class'] = empty($attributes['class']) ? 'first' : ($attributes['class'] . ' first');
+        $attributes['class'] .= ' first';
       }
       if ($i == $num_items - 1) {
-        $attributes['class'] = empty($attributes['class']) ? 'last' : ($attributes['class'] . ' last');
+        $attributes['class'] .= ' last';
       }
       $output .= '<li' . drupal_attributes($attributes) . '>' . $data . "</li>\n";
     }