Hydroxylated polychlorinated biphenyls (PCBs) have been identified in wildlife and human samples. Most of these compounds are highly chlorinated (penta-hepatachloro) and contain a single meta- or para-hydroxyl group. Using the Cadogan coupling procedure, the following hydroxy-PCBs congeners were synthesized: 2,3,3',4',5-pentachloro-4-biphenylol, 2,3',4,4',5-pentachloro-3-biphenylol, 2',3,3',4',5-pentachloro-4-biphenylol, 2,2',3',4,4'-pentachloro-3-biphenylol, 2,2',3,3',4',5-pentachloro-4-biphenylol, 2,2',3',4,4',5-hexachloro-3-biphenylol, 2,2',3,4',5,5'-hexachloro-4-biphenylol, 2,2',3,3',4',5,5'-heptachloro-4-biphenylol, 2,2',3',4,4',5,5'-hepatachloro-3-biphenylol, 2,2',3,4',5,5',6-heptachloro-4-biphenylol. Many of these compounds have been detected as residues in human serum and current studies are investigating their activities as agonists and antagonists for several endocrine-mediated responses.