Based on animal carcinogenesis studies, benzoin and caprolactam have been classified as noncarcinogens. The genetic toxicity of both compounds has been thoroughly evaluated in short-term in vitro bioassays. Genetic activity profiles and corresponding data listings and summaries are presented for benzoin and caprolactam. Generally weak positive responses were obtained with benzoin only in mammalian cell mutagenesis and cell transformation assays. In the case of caprolactam, reproducible positive responses were obtained for somatic mutations in Drosophila and for mammalian cell transformation (in different cell lines) at high dose levels. Since the chemical structures of benzoin and caprolactam do not suggest the potential for genotoxicity, these responses may be associated with nonspecific toxicity. The overwhelming majority of short-term test data suggest that, in accordance with animal cancer data, benzoin and caprolactam are not genotoxic. (Copyright (c) Elsevier Science Publishers B. V. (Biomedical Division).)