Index: wp-includes/class-wp-xmlrpc-server.php
===================================================================
--- wp-includes/class-wp-xmlrpc-server.php	(revision 19632)
+++ wp-includes/class-wp-xmlrpc-server.php	(working copy)
@@ -64,6 +64,7 @@
 			'wp.getMediaItem'		=> 'this:wp_getMediaItem',
 			'wp.getMediaLibrary'	=> 'this:wp_getMediaLibrary',
 			'wp.getPostFormats'     => 'this:wp_getPostFormats',
+			'wp.setPostTerms'		=> 'this:wp_setPostTerms',
 
 			// Blogger API
 			'blogger.getUsersBlogs' => 'this:blogger_getUsersBlogs',
@@ -1702,6 +1703,75 @@
 		return $formats;
 	}
 
+	/**
+	 * Set post terms
+	 *
+	 * @uses wp_set_object_terms()
+	 * @param array $args Method parameters. Contains:
+	 *  - int     $blog_id
+	 *  - string  $username
+	 *  - string  $password
+	 *  - int     $post_id
+	 *  - array   $content_struct contains term_ids with taxonomy as keys
+	 *  - bool    $append
+	 * @return boolean true
+	 */
+	function wp_setPostTerms( $args ) {
+		$this->escape($args);
+
+		$blog_id            = (int) $args[0];
+		$username           = $args[1];
+		$password           = $args[2];
+		$post_ID            = (int) $args[3];
+		$content_struct     = $args[4];
+		$append             = $args[5] ? true : false;
+
+		if ( ! $user = $this->login( $username, $password ) )
+			return $this->error;
+
+		do_action( 'xmlrpc_call', 'wp.setPostTerms' );
+
+		$post = wp_get_single_post( $post_ID, ARRAY_A );
+		if ( empty( $post['ID'] ) )
+			return new IXR_Error( 404, __( 'Invalid post ID.' ) );
+
+		$post_type = get_post_type_object( $post['post_type'] );
+
+		if( ! current_user_can( $post_type->cap->edit_post , $post_ID ) )
+			return new IXR_Error( 401, __( 'Sorry, You are not allowed to edit this post.' ) );
+
+		$post_type_taxonomies = get_object_taxonomies( $post['post_type'] );
+
+		$taxonomies = array_keys( $content_struct );
+
+		// validating term ids
+		foreach( $taxonomies as $taxonomy ) {
+			if( ! in_array( $taxonomy , $post_type_taxonomies ) )
+				return new IXR_Error( 401, __( 'Sorry, one of the given taxonomy is not supported by the post type.' ) );
+
+			$term_ids = $content_struct[$taxonomy];
+			foreach ( $term_ids as $term_id ) {
+
+				$term = get_term( $term_id, $taxonomy );
+
+				if ( is_wp_error( $term ) )
+					return new IXR_Error( 500, $term->get_error_message() );
+
+				if ( ! $term )
+					return new IXR_Error( 403, __( 'Invalid term ID' ) );
+			}
+		}
+
+		foreach( $taxonomies as $taxonomy ) {
+			$term_ids = $content_struct[ $taxonomy ];
+			$term_ids = array_map( 'intval', $term_ids );
+			$term_ids = array_unique( $term_ids );
+			wp_set_object_terms( $post_ID , $term_ids, $taxonomy , $append);
+		}
+
+		return true;
+	}
+
 	/* Blogger API functions.
 	 * specs on http://plant.blogger.com/api and http://groups.yahoo.com/group/bloggerDev/
 	 */