In the present study, fresh blood obtained from six healthy adult male donors was investigated for erythrocyte malondialdehyde (MDA) formation and antioxidative enzyme activity. Plasma and erythrocyte membrane lipid peroxidation were measured by MDA formation. Erythrocyte superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels were determined in whole blood stored for transfusion purposes. Erythrocyte and plasma MDA levels increased significantly during the storage period from day 3 to day 19 and, after that, stayed unchanged. Erythrocyte MDA increased 100% on day 7 when compared to day 1. The GSH-Px activity significantly decreased after day 9 and SOD decreased after day 13. The reduction in enzyme activities continued until day 27. Our results showed significant alteration in erythrocyte membrane and plasma MDA formation and intracellular antioxidant enzyme status in whole blood used for transfusion. However, we do not know whether such alterations have clinical importances for the recipient.