A novel phenol sulfotransferase (PST) was detected in bovine liver microsomal membrane fraction. The enzyme was found to be capable of catalyzing the sulfation of simple phenolic compounds, with 3'-phosphoadenosine-5'-phosphosulfate as the sulfate donor. Detergent extracted PST showed a pH optimum of 5.7 and, among the simple phenols tested, the PST exhibited highest activity toward alpha-naphthol. No activities were detected when tyrosine and its derivatives were used as substrates. Both 2,6-dichloro-4-nitrophenol and chlorpromazine were capable of inhibiting the activity of the PST toward p-nitrophenol with inhibition Coefficient50 values of 100 nM and 4 mM, respectively.