Many laboratories have characterized the electrophilic metabolites of chemical carcinogens and their covalently bound adducts with genomic DNA in vivo. Recent studies from our laboratory have shown that enzymatic sulfonation of members of several classes of proximate carcinogens containing C- or N-hydroxy groups converts them to electrophilic, mutagenic, and carcinogenic sulfuric acid ester metabolites in mouse liver. These compounds form the subject of this report.