The mutagenic activity of some dyes, derivatives of anthraquinone and aniline, was studied in tests on Salmonella typhimurium. A total of 16 anthraquinones and 9 anilines were tested. It was detected that 7 anthraquinone dyes did not induce gene mutations in Salmonella. Two substances, 2-chlor-anthraquinone and 1-nitro-anthraquinone, showed a medium-strength effect. Seven dyes (1-methyl-amino-4-bromanthraquinone, leuko-1,4-diamino-anthraquinone, 1,5-diaminoanthraquinone, 1-chlor-anthraquinone, 1,2- and 1,8-dihydroxyanthraquinone, 1-chlor-4-benzil-amino-anthraquinone) were weak mutagens. The metabolic activation system was not effective, i.e. the dyes studied are mutagens with a direct action. A dose dependence was detected. The main mechanism of induction of gene mutations is frameshift. From nine dyes of the aniline series, three compounds showed a weak mutagenic effect: 3-nitro-aniline, anilin-3-sulpho-acid and 4-nitroaniline-2-sulpho-acid. The latter substance is an indirect mutagen. The other two are direct ones. The mechanism of induction of gene mutations is frameshift.