This study, designed to investigate antioxidant the erythrocyte anti-oxidant status in malignant and benign breast tumours, was carried out on 38 patients. Based upon their histopathology, the patients were grouped as breast carcinoma (n=23) and benign breast disease (n=15). Of the 23 patients with breast carcinoma 14 had only ductal, 2 had lobular and 7 had ductal + lobular carcinoma. 14 patients with breast carcinoma had axillary metastasis and 9 had no metastasis. Patients in the malignant, group were aged between 38 and 80 years (58.61±13.38); those in the benign group were aged between 20 and 46 years (37±7.42). Heparinised blood samples, drawn preoperatively after an overnight fast, were analysed for erythrocyte CuZn superoxide dismutase (CuZn, SOD), glutathione peroxidase (GSH Px) and glutathione (GSH) values. Erythrocyte GSH-Px values were found to be significantly higher in the malignant group in comparison with the benign group (0.01 >P>0.001 ). CuZn SOD activity and GSH concentration were found to be higher , but not at significant levels, in the malignant group. Measuring the tissue levels of antioxidant status components would serve better for the evaluation of antioxidant profiles in patients with breast carcinoma and benign breast diseases.