Quinone derivatives of the polycyclic aromatic hydrocarbon, anthracene, were investigated for their ability to induce 7-ethoxyresorufin-O-deethylase (EROD) activity in a cell line from rainbow trout liver, RTL-W1. Of the 11 anthracene quinones tested, five were capable of inducing EROD activity. From most to the least potent, the order of induction potency, based on EC50 values, was 2,6-dihydroxyanthraquinone = 1,2,4trihydroxyanthraquinone < 1,2-dihydroxyanthraquinone = 1,3-dihydroxyanthraquinone = 2-hydroxyanthraquinone. The 1,2,10-trihydroxylated anthracene also induced EROD activity whereas anthraquinone did not, indicating that the quinone structure alone was not adequate for EROD induction to occur. The current results show that UV irradiation of an AhR-inactive PAH, such as anthracene, can yield derivatives that are AhR active and induce EROD activity in fish cells and presumably in fish. Thus, responses mediated by the AhR and/or P4501A should be considered in the environmental risk assessment of UV/PAH interactions.