Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 15497)
+++ wp-includes/query.php	(working copy)
@@ -2305,10 +2305,18 @@
 		if ( ! empty($q['meta_key']) )
 			$where .= $wpdb->prepare(" AND $wpdb->postmeta.meta_key = %s ", $q['meta_key']);
 		if ( ! empty($q['meta_value']) ) {
-			if ( empty($q['meta_compare']) || ! in_array($q['meta_compare'], array('=', '!=', '>', '>=', '<', '<=')) )
+			if ( empty($q['meta_compare']) || ! in_array($q['meta_compare'], array('=', '!=', '>', '>=', '<', '<=', 'in')) )
 				$q['meta_compare'] = '=';
-
-			$where .= $wpdb->prepare("AND $wpdb->postmeta.meta_value {$q['meta_compare']} %s ", $q['meta_value']);
+			
+			if ( 'in' == $q['meta_compare'] ) {
+					if ( !is_array($q['meta_value']) )
+						$q['meta_value'] = preg_split('!,\[\r\n\t ]+!', $q['meta_value']); 
+					$meta_field_types = substr(str_repeat(',%s', count($q['meta_value'])), 1);
+					$where .= $wpdb->prepare("AND $wpdb->postmeta.meta_value IN($meta_field_types) ", $q['meta_value']);
+					unset($meta_field_types);
+			}
+			else
+				$where .= $wpdb->prepare("AND $wpdb->postmeta.meta_value {$q['meta_compare']} %s ", $q['meta_value']);
 		}
 
 		// Apply filters on where and join prior to paging so that any