The single and combined effects of methylmercury and Arochlor 1260 were investigated in experimental quail treated chronically with the two compounds at low and high doses. A series of metabolic and biochemical biomarkers were evaluated together with mercury and PCB accumulation to pinpoint the effects of treatment with one or both chemicals. Methylmercury alone was associated with a decrease in serum cholesterol. Less PCBs were accumulated in tissues when Arochlor 1260 was combined with methylmercury than when the former was administered alone. Liver monooxygenase (MFO) activity was depressed 50% more in the presence of methylmercury than with Arochlor 1260 alone. Single or combined treatment with high doses of the two compounds resulted in similar degrees of DNA damage. This approach was found to provide a good picture of the interaction between environmental contaminants.