Cuprozinc superoxide dismutase(CuZn-SOD) from human erythrocytes was purified by a procedure involving Cu²⁺ chelate affinity chromatography.It was shown in three experiments that the special chromatography held a number of important advantages for protein purification,such as a high rate of repeating performance and a large protein capacity. The purified enzyme,with a specific activity of 3073 U/mg protein, was tested for homogeneity by activity-stained and SDS gel electrophoresis.Accompanied by the study,a simple and efficient method was worked out for assessing the homogeneity of CuZn-SOD using its ratio of the absorbence at 260nm to that at 280nm.