Thyroid hormone controls various metabolic functions. Hypothyroidism is a clinical condition with reduced thyroid activity. Study intended to appraise the oxidative stress in various degree of Hypothyroidism. Recently detected hypothyroid patients were grouped according to the TSH level into three categories as Group I: TSH level 6-20uIU/dl, Group II TSH level 21-40uIU/dl: & Group III TSH level above 40uIU/dl. Oxidative stress has been assessed by detecting Total antioxidant capacity (TAC) of hypothyroid patients, compared to euthyroid control. Total Antioxidant Capacity was reported to be reduced at baseline in all three groups of hypothyroid patients. After six weeks of thyroxin replacement therapy TAC level has been found to be increased. The reduction of Total Antioxidant Capacity in hypothyroid patients reflects increase oxidative stress in hypothyroidism. Oxidative stress has been associated with early aging and precipitating factor of many anomalous metabolic reactions. Consequently antioxidant therapy should also be included with thyroid replacement therapy.