The anti-psoriatic compound anthralin (cignolin) was determined to exhibit a strong cytostatic activity on HeLa-Köln cells; an ED50 concentration of 1.2 microM are cytotoxic for the cells. These growth-inhibition data were confirmed by thymidine-uptake experiments. The drug anthralin was determined to be neither direct a mutagen nor a premutagen in the Ames test using Salmonella typhimurium strain TA 100 (anthralin-concentration = 5 microM). Moreover, this compound was a strong inhibitor of benzo(a)pyrene monooxygenase, an enzyme which causes the metabolic conversion of premutagens to mutagens. These data demonstrate anthralin to be an anti-psoriatic compound devoid of mutagenic property in vitro with regard to base-pair substitutions and provided at least with some antimutagenic potential.