Suppressed superoxide dismutase activity, which is responsible for the dismutation of superoxide anion to hydrogen peroxide, is known to be one of the factors leading to lipid peroxidation in the erythrocyte membrane structures in the patients with end stage renal disease. In this study, copper and zinc levels were determined in the erythrocytes and plasma from 14 hemodialysis patients to explain the decreased activity of superoxide dismutase in erythrocytes. Before dialysis, superoxide dismutase, copper and zinc levels in erythrocytes were lower than those from healthy controls. Superoxide dismutase activity was normalized perfectly after hemodialysis. Copper level in the erythrocytes was normalized after hemodialysis, but its level was still lower than that in healthy controls. Zinc level in the erythrocytes was not changed after hemodialysis. Before hemodialysis, copper and zinc levels in plasma were higher than those from healthy controls. Copper level in the plasma was higher after hemodialysis than before hemodialysis. Zinc level in the plasma was not changed after hemodialysis. It is suggested that copper levels in erythrocytes from patients with hemodialysis affects partially to the superoxide dismutase activity, and superoxide dismutase activity is influenced more by copper levels than by zinc levels during hemodialysis.