Accumulation of cadmium (Cd), mercury (Hg), lead (Pb), chromium (Cr), hexachlorobenzene, gamma-HCH, DDTs, and PCBs has been investigated in the muscle of Ameiurus melas sampled during the same period from Lake Corbara, Alviano, and Trasimeno. Glutathione content and the enzymatic activities of glutathione reductase, glutathione peroxidase, catalase, glutathione S-transferase, and glyoxalase I were examined in gills, liver, and kidneys of each specimen. Catfish from Alviano, compared to those of Corbara and Trasimeno, showed the highest contamination of DDTs and PCBs and the lowest levels of biochemical parameters. Most likely, OCPs and PCBs content might be responsible for the compromised antioxidant status in these specimens.