In the present study we have assayed antioxidant enzymatic systems in erythrocytes from subjects with chronic cerebrovascular disease to correlate their involvement in red cell deformability. A significant decrease of glutathione peroxidase, reductase, catalase and superoxide dismutase activities has been found in human red blood cells from patients with chronic cerebrovascular disease when compared to the control group. The decrease in antioxidant enzymatic systems found in these patients was accompanied by reduced cellular resistance to hydrogen peroxide. An altered balance between the partially reduced forms of oxygen metabolism and the antioxidant enzymatic systems could play a crucial role in the haemorheological alteration frequently occurring in subjects affected by chronic cerebrovascular disease.