Although various types of path indexes -- indexes on path expressions -- have been proposed for efficient processing of object-oriented queries, conventional join algorithms do not effectively utilize them. We propose a new join algorithm called OID join algorithm that effectively utilizes (multiple) path indexes in object-oriented databases. When (multiple) path indexes are available for a query, OID join algorithm may reduce the query evaluation cost significantly by taking full advantage of the path indexes. We present cost analysis for OID join algorithm and compare it with those of conventional ones.