Most chemical carcinogens are ultimate carcinogens. Polyaromatic hydrocarbons, such as benzo(a)pyrene, are activated by mixed-function oxidases, the key components of which are cytochromes P-450. Identification and quantitation of cytochrome P-450 isozymes are essential to understanding the role of cytochrome P-450 in the primary process of chemical carcinogenesis and individual differences in sensitivity to chemical carcinogens. Our approach is to prepare monoclosan antibodies (MAbs) specific for individual and classes of cytochrome P-450. In addition to the MAbs directed to cytochromes P-450 of rats treated with phenobarbital (PB-P-450), 3-methylcholanthrene (MC-P-450), and Beta-naphthoflavone (BNF-P-450), we prepared and characterized MAbs to pregnenolone 16-Alpha-carbonitrile induced PCN-P-450 and environmentally induced marine fish cytochrome P-450. Among 11 MAbs to PCN-P-450, 8 were specific to PCN-P-450 and 3 cross-reacted with PB-P-450E. We also prepared MAbs to uninduced forms of cytochrome P-450. Among 9 MAbs to Scup-P-450, 8 were specific to Scup-P-450 and one recognized both Scup-P-450 and rat liver MC-P-450. MAbs to uninduced forms of cytochrome P-450 were all IgM types. These MAbs have been utilized to phenotype and purify cytochromes P-450 from tissues and organs of animals and humans.