A series of N-oxidized derivatives of aniline (la), 2'-methyl-4-aminobiphenyl (5a), and the carcinogens o-toluidine (lb) and 3, 2'-dimethyl-4-aminobiphenyl (5b) were prepared and tested for mutagenic activity toward S. typhimurium. The compounds tested were the hydroxylamines 2a, b and 6a, b; C-nitroso compounds 3a, b and 7a, b; and the hydroxamic acids 4a, b and 8a, b derived from the amines la, b and 5a, b, as well as the parent amines ...