The 'antioxidant' enzymes superoxide dismutase (SD), catalase and glutathione peroxidase (GSH-Px) were found greatly elevated in red blood cells of subjects with beta-thalassaemia minor and similar to normal values in red blood cells of subjects with beta-thalassaemia major. These findings allows us to speculate that red cells in beta-thalassaemia minor react to the increased oxidant threat with augmented antioxidant enzyme activities. The normal levels of antioxidant enzymes in beta-thalassaemia major seem to be due to the presence of normal red cells owing to multiple transfusions.