To obtain a comprehensive profile of the erythrocyte antioxidant defense potential during aging, we investigated copper-zinc superoxide dismutase (CuZn-SOD), seleno-dependent glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-RD), and glutathione-S-transferase (GSH-S-T) activities in human erythrocytes from 167 apparently healthy subjects, ages one month to 63 years (102 females, 65 males). We found a negative correlation between age and activities of CuZn-SOD (r = 0.362, P less than 0.001), GSSG-RD (r = 0.549, P less than 0.001), and GSH-S-T (r = 0.575, P less than 0.001). In contrast, we found a positive correlation between age and GSH-Px activity (r = 0.401, P less than 0.001). To evaluate aging changes, we divided the subjects into five groups: Group 1 (newborn-age one year), Group 2 (1-11 years), Group 3 (11-25 years), Group 4 (25-40 years), and Group 5 (40-63 years). Significant age-related modifications in erythrocyte enzyme activities appeared in Group 3 for CuZn-SOD, GSSG-RD, and GSH-Px activity, whereas for GSH-S-T activity age-related modifications appeared in Group 2. We found no sex-related differences in erythrocyte CuZn-SOD, GSSG-RD, GSH-Px, and GSH-S-T activities.