Incubations of phenylethylamine and 11 of its analogues with Cunninghamella bainieri have been performed. 2. Products of all major routes of mammalian metabolism including ring and aliphatic hydroxylation, oxidative deamination, N-oxidation, N-dealkylation, and conjugation were found in extracts of the fungal incubation broths. 3. Metabolism was influenced by the nature and degree of substitution.