To evaluate potential interactive effects of metals and polycyclic aromatic hydrocarbons (PAHs) on biomarker responses, groups of the freshwater fish crucian carp (Carassius auratus) were exposed to single and binary combinations of copper (Cu) (0.01-0.16 mg L-1) with fluorene (Fl) or fluoranthene (Fluo) (2-10 mg kg^-1) for 96 h. Dose-dependent increases in the activities of phases I and II metabolic enzymes [7-ethoxyresorufin O-deethylase (EROD) and glutathione-S-transferase (GST), respectively] were observed in fish liver exposed to Fl and Fluo, but these enzyme activities did not differ significantly from the controls when co-treated with higher concentrations of Cu, suggesting an inhibiting interaction on the metabolic enzymes. Although Cu did not alter catalase (CAT) activity, CAT activity was decreased in fish liver exposed to the two PAHs alone or in combination with Cu. Although metallothionein (MT) content in gills was significantly increased following exposure to Cu alone or in combination with Fl and Fluo, the induction folds of MT decreased under co-exposure. Co-exposures to these chemicals invoked complex biomarker responses in fish liver and gills. These results highlight the need for careful consideration of the interactive effects of multiple environmental stressors on fish.