Two suspect aneugens (hydroquinone and econazole nitrate) were examined for their ability to induce micronuclei in a number of V79 Chinese hamster cell lines which express rat cytochrome P-450 cDNAs. Hydroquinone elevated micronucleated cell frequencies in a dose-dependent manner in cell lines V79, XEM2 (expresses CYP1A1) and SD1 (expresses CYP2B1). Econazole nitrate was an effective inducer of micronuclei over a narrow dose range in cell lines V79, XEM2 and XEMd-MZ (expresses CYP1A2). The different cell lines showed similar responses to the test agents, indicating that hydroquinone is not a substrate for biotransformation by rat CYP1A1 or CYP2B1, nor is econazole nitrate biotransformed by rat CYP1A1 or CYP1A2.