Administration of 3H-labeled N-hydroxy-4-acetylaminobiphenyl (N-OH-AABP) to male Wistar rats with or without prior partial hepatectomy (PH) resulted in covalent binding of 3H activity to liver macromolecules. Pretreatment with the sulfotransferase inhibitor pentachlorophenol (PCP) 45 min before administration of the arylhydroxamic acid strongly decreased the covalent binding. Analysis of aminobiphenyl adducts after TFA hydrolysis of DNA and RNA showed that PCP decreased the formation of both the N-acetylated adduct N-[deoxy)guanosin-8-yl)-4-acetylaminobiphenyl [(d)G-C8-AABP] and the deacetylated adduct N-[deoxy)-guanosin-8-yl)-4-aminobiphenyl [(d)G-C8-ABP] by 60-80%. In incubations with hepatocytes from male Wistar or Sprague-Dawley rats, omission of inorganic sulfate also strongly decreased the covalent binding of 3H-labeled N-OH-AABP to RNA and protein. Analysis of RNA adducts showed a 70-80% decrease in the formation of G-C8-ABP in the absence of sulfate. Another, as yet unidentified, adduct was only slightly decreased. Similar results were obtained with the structurally related carcinogen N-hydroxy-4'-fluoro-4-acetylaminobiphenyl (N-OH-FAABP). Pretreatment with PCP decreased the incidence of gamma-glutamyltranspeptidase-positive foci in the liver of male rats when analyzed 30 days after a single injection of N-OH-AABP or N-OH-FAABP by 60 and 80% respectively. Thus, both N-acetylated and deacetylated RNA and DNA adducts of N-OH-AABP in rat liver are formed by sulfation and this metabolic activation pathway is responsible for the formation of genotoxic metabolites involved in the generation of preneoplastic cells.