We evaluated pyrogallol cytotoxicity using Escherichia coli strains that express mammalian catalase gene derived from catalase mutant mice (Cs(b)) and wild-type (Cs(a)), and pyrogallol mutagenicity by Ames test. Pyrogallol was more toxic to Cs(b) rather than to Cs(a) (p < 0.05), while catalase, superoxide dismutase and ascorbic acid decrease the toxic effect. Pyrogallol also showed mutagenic effect (mutagenic index = 3.8 for 10 micromol pyrogallol/plate) while ascorbic acid (19.4% reduction, p < 0.001) and naringin (35.1% reduction, p < 0.001) played a protective role against it. Pyrogallol cytotoxicity and mutagenicity seem to be attributable, at least in part, to reactive oxygen species formation. This study also suggests that newly established catalase mutant E. coli is probably useful in hazard identification of oxidative chemicals.