A human homologue of the bacterial DNAJ heatshock protein, HDJ-2, was isolated from a human umbilical vein endothelial cDNA library using a monoclonal antibody which reacts specifically to human endothelial cells and monocytes. This cDNA clone consists of 1469 nucleotides with an open reading frame of 1191 nucleotides. HDJ-2 shares significant homology with Escherichia coli heat shock protein DNAJ, as well as the yeast homologues Sec63, YDJ1, SCJ1 and SIS1. This homology suggests HDJ-2 may be involved in protein folding and/or transport.