diff --git a/core/user_api.php b/core/user_api.php
index 883f2f2..2e1ef90 100644
--- a/core/user_api.php
+++ b/core/user_api.php
@@ -131,6 +131,19 @@ function user_cache_array_rows( $p_user_id_array ) {
 	return;
 }
 
+function user_cache_all() {
+	global $g_cache_user;
+
+	$t_user_table = db_get_table( 'user' );
+	$t_query = "SELECT * FROM $t_user_table";
+	$t_result = db_query_bound( $t_query );
+
+	while( $t_row = db_fetch_array( $t_result ) ) {
+		$g_cache_user[(int) $t_row['id']] = $t_row;
+	}
+	return $g_cache_user;
+}
+
 # --------------------
 # Cache an object as a bug.
 function user_cache_database_result( $p_user_database_result ) {
@@ -730,6 +743,12 @@ function user_get_row( $p_user_id ) {
 }
 
 # --------------------
+# return all users
+function user_get_all() {
+	return user_cache_all();
+}
+
+# --------------------
 # return the specified user field for the user id
 function user_get_field( $p_user_id, $p_field_name ) {
 	if( NO_USER == $p_user_id ) {
diff --git a/core/xmlhttprequest_api.php b/core/xmlhttprequest_api.php
index 7c9e243..307a31a 100644
--- a/core/xmlhttprequest_api.php
+++ b/core/xmlhttprequest_api.php
@@ -57,6 +57,22 @@ function xmlhttprequest_filter_by_prefix( $p_set, $p_prefix ) {
 }
 
 /**
+ * Filter a set of strings by finding strings that match a case-insensitive substring.
+ * @param array $p_set An array of strings to search through.
+ * @param string $p_substr The substring to filter by.
+ * @return array An array of strings which match the supplied substring.
+ */
+function xmlhttprequest_filter_match( $p_set, $p_substr ) {
+	$t_matches = array();
+	foreach ( $p_set as $p_item ) {
+		if( utf8_strpos( utf8_strtolower( $p_item ), utf8_strtolower( $p_substr ) ) !== false ) {
+			$t_matches[] = $p_item;
+		}
+	}
+	return $t_matches;
+}
+
+/**
  * Echos a serialized list of platforms starting with the prefix specified in the $_POST
  * @return null
  * @access public
@@ -97,3 +113,21 @@ function xmlhttprequest_os_build_get_with_prefix() {
 
 	echo json_encode( $t_matching_entries );
 }
+
+/**
+ * Echos a serialized list of Users starting with the prefix specified in the $_POST
+ * @return null
+ * @access public
+ */
+function xmlhttprequest_username_get_with_prefix() {
+	$f_username = gpc_get_string( 'username' );
+
+	$t_users = user_cache_all();
+	foreach( $t_users AS $t_user ) {
+		$t_unique_entries[] = $t_user['username'];
+	}
+
+	$t_matching_entries = xmlhttprequest_filter_match( $t_unique_entries, $f_username );
+
+	echo json_encode( $t_matching_entries );
+}
diff --git a/manage_user_page.php b/manage_user_page.php
index 3231f7b..484031b 100644
--- a/manage_user_page.php
+++ b/manage_user_page.php
@@ -380,7 +380,7 @@ for ($i=0;$i<$user_count;$i++) {
 			<fieldset>
 				<span class="field-container">
 					<span class="label"><label for="username"><?php echo lang_get( 'username' ) ?></label></span>
-					<span class="input"><input id="username" type="text" name="username" value="" /></span>
+					<span class="input"><input id="username" type="text" name="username" value="" class="autocomplete" /></span>
 				</span>
 				<span class="submit-button"><input type="submit" class="button" value="<?php echo lang_get( 'manage_user' ) ?>" /></span>
 			</fieldset>