This bioassay utilizes cultured Hepa-lclc7 (Hepa-1) mouse hepatoma cells to assess the CYPlA1-inducing potency or cytotoxicity of pure test chemicals or environmental samples. In the Hepa-l induction test , the CYPlA1-inducing potency of the test sample is detected as increased aryl hydrocarbon hydroxylase (AHH) and 7-ethoxyresorufin O-deethylase (EROD) activities.