BACKGROUND: The association between hypertension and diabetes has been linked to increased oxidative stress with age. This study was to examine the level of age-dependent alterations in antioxidant defense system between patients having hypertension and/or type-2 diabetes. METHODS: The study was conducted at the Ahmadu Bello University Teaching Hospital, Zaria-Nigeria, using 200 Subjects recruited from the cardiology, endocrinology and outpatient clinics. They were divided into four groups of 50 subjects each, namely: Diabetic group (DG), hypertensive (HG) and hypertensive-diabetic group (HDG) as cases. The control group (CG) was non-diabetic normotensive subjects. They were all stratified into six age-ranges namely 20-29, 30-39, 40-49, 50-59, 60-69, 70-79 years. Oxidative stress markers (lipid peroxidation, antioxidant vitamins and elements, enzymatic and non-enzymatic antioxidant) were measured in the blood sample collected from all subjects in each age group within the study groups. RESULTS: The results in the DG, HG and HDG, showed that the percentage decrease in enzymatic antioxidants and antioxidant vitamins with age were significantly (P <0.05) higher than 10.8 and 20.0 respectively when compared to the CG, whereas, the level of decrease in serum Selenium at same age range was significantly higher than 52.8 . The level of lipid peroxidation in the cases was observed to be significantly (P <0.05) higher than 89.9 when compared to the mean reference values (2.94 +/- 0.05 nmol/ml) of the CG at same age range. Also, the decrease levels of endogenous antioxidants were observed to be directly related to aging. CONCLUSION: The result obtained demonstrates the percentage age-dependent alteration in oxidative stress markers. The percentage decrease in the antioxidant levels during aging could be an explanation to the possible link, underlying the complication of type-2 diabetes and hypertension in this locale. Hence, antioxidants supplements may be useful in the management of the diseases during aging.