The aim of this study was to estimate the effect of aquatic cadmium and lead pollution on superoxide dismutase (SOD) activity and lipid peroxidation in fish. The study used the fish species Cyprinus carpio L., Oncorhynchus mykiss Walbaum, and Acipenser baeri Brandt. SOD activity was measured by the adrenaline method. Lipid peroxidation was measured by determining malondialdehyde (MDA) concentrations. Cd and Pb were determined by graphite furnace spectrometry (GF-AAS). In the examined fish, measured concentrations were: Cd (0.002-0.022 mg kg^-1 w.w.), Pb (0.002-0.021 mg kg-1 w.w), SOD (1.20-5.84 U mg^-1 protein), and MDA (0.83-6.71 nmol mg^-1 protein). At low metal levels in the blood and muscle, higher SOD activity occurred, which reduced lipid peroxidation. Increased metal concentrations increased lipid peroxidation in the three fish species and simultaneously reduced SOD activity.