4, 4′‐(Methylene‐14C)bis[N, N‐dimethylbenzenamine] (2), 2, 4‐14C, 6‐trimethylbenzenamine hydrochloride (7), and 4‐chloro‐2‐(methyl‐14C)benzenamine hydrochloride (18) were synthesized for an investigation of the metabolism of carcinogenic compounds. Evaluations of synthetic routes led to the following preferred methods: the LiAlH4‐AlCl3 reduction of carbonyl‐labeled Michler's ketone for 2, the Hofmann‐Martius rearrangement of the salt formed from 2, 6‐dimethyl‐benzenamine and iodomethane‐14C for 7, and the nitration of (methyl‐14C)benzene followed by reduction with stannous chloride in hydrochloric acid for 18. The free bases of 7 and 18 were isolated from complex product mixtures by preparative thin‐layer chromatography, but the free base of 7 was not completely separated from a tetramethylbenzenamine.