1. Malondialdehyde (MDA) levels of erythrocyte membranes of sickle-cell disease patients were measured as an indicator of peroxidative damage and allopurinol was used as a lipid peroxide scavenger. 2. Incubating sickle-cell erythrocytes with allopurinol significantly reduced MDA levels of erythrocyte membranes compared with before-treatment values. 3. Allopurinol seems to reduce the peroxidative damage in sickle-cell erythrocytes, but the mechanism is still unknown.