Human hydroxysteroid sulfotransferase, human phenol-sulfating form of phenol sulfotransferase, rat hydroxysteroid sulfotransferase a and rat phenol sulfotransferase IV were expressed in Escherichia coli. Cytosol preparations of transformed bacteria were used as activating systems in mutagenicity tests with Salmonella typhimurium TA98. All test compounds, 1-hydroxymethylpyrene, 2-hydroxymethylpyrene, 1-(1-pyrenyl)ethanol, 9-hydroxymethylanthracene, 7-hydroxymethyl-12-methylbenz[a]anthracene and 4H-cyclopenta[def]chrysen-4-ol, were activated by both hydroxysteroid sulfotransferases investigated. However, 1-(1-pyrenyl)ethanol was 67-fold more efficiently activated by the human enzyme, whereas 7-hydroxymethyl-12-methylbenz[a]anthracene was 27-fold more efficiently activated by the rat enzyme. The phenol sulfotransferases showed relatively low activities with the benzylic alcohols investigated. The only exception was 4H-cyclopenta[def]chrysen-4-ol, which was activated efficiently by rat phenol sulfotransferase IV. We had previously tested the ability of rat and human hepatic cytosol preparations to activate the same compounds. The results of a statistical analysis suggest that the activities of human hydroxysteroid sulfotransferase, rat hydroxysteroid sulfotransferase a and phenol sulfotransferase IV can account for a substantial portion of the activation of benzylic alcohols in human, female rat and male rat liver, respectively.