Using direct specific analytical techniques microsomal metabolism of N-benzyl-4-substituted anilines has been investigated and found to include both N- and C-oxidation. N-Debenzylation was observed with all substrates and species examined. N-Oxidation usually yielded aryl nitrones, although the N-hydroxy derivative of the 4-chloro-substituted substrate was identified in some species. This is the first direct evidence of microsomal N-hydroxylation of a secondary aniline. The metabolic formation of amides from these secondary amines was observed and is believed to be a novel class of metabolite for these substrates.