Induction of 6-thioguanine-resistant mutations was studied in Chinese hamster V79 cells treated with nitrofurylacrylic acid under aerobic and hypoxic conditions. The results obtained demonstrated that the mutagenic activity of this substance, less significant in aerobic conditions, was very high under hypoxic conditions. A gradual increase in mutation frequencies according to the applied concentrations of nitrofurylacrylic acid was observed, the maximal values being at 0.8 mg of the substance per 1 ml of growth medium. The mutagenic effects of nitrofurylacrylic acid were independent of its cytostatic effect that was higher in aerobic than hypoxic conditions. Mutagenic capacity of this substance found in vitro in mammalian V79 cells suggests its possible carcinogenic potential in vivo under conditions favorable for metabolic activation of this nitrofuran-derived compound.