Objective: To study the antioxidative prospective of diuretics (hydrochlorothiazide) or β-blockers (atenolol) in long-term hypertension therapy. Methods: Enzymatic and non-enzymatic antioxidants , and lipid peroxidation in blood was measured in hypertensive patients on long-term medication with either diuretics or β-blockers , and they were compared with agematched untreated hypertensive patients , and normal subjects. Results: Plasma levels of lipid peroxidation as thiobarbituric acid reactive substances (TBARS) in untreated hypertensive patients were significantly (P < 0. 05) higher while the levels of enzymatic and non-enzymatic antioxidants were significantly lower (P < 0. 05) as compared to hypertensive patients with medication,and normal subjects. Between the two drug treated hypertensive groups, although no significant (P < 0.05) differences were observed in blood pressure , a significant improvement in the status of enzymatic ( superoxide dismutase , catalase and glutathione peroxidase) and non-enzymatic (vitamin C , vitamin E , β-carotene and reduced glutathione) antioxidants were observed in atenolol treated group compared to untreated hypertensive patients , and patients treated with hydrochlorothiazide. Conclusion: The results of the present study suggest that atenolol has better antioxidative capacity by protecting the enzymatic and non-enzymatic antioxidants when compared with hydrochlorothiazide therapy. © 2010 Elsevier B.V., All rights reserved.