There is growing evidence that oxidative stress contributes to the pathogenesis of hypertension. Our aim was to measure oxidative stress in hypertensive subjects, and assess the potential confounding influences of antihypertensive therapy. Serum malondialdehyde and antioxidant levels were estimated in patients at the time of presentation and also after a antihypertensive therapy for 3 months. During the period of study no antioxidant/s was given to the patients and control subjects. Mean blood pressure values were altered in the hypertensive patients following antihypertensive therapy from their respective values observed at the time of presentation. Serum malondialdehyde levels were significantly higher in the hypertensive patients in comparison to control cases. The antioxidant activity of enzymes super oxide dismutase, glutathione and non enzymatic antioxidant levels of vitamins E and C were significantly lower in patients compared to controls. After 3 months of antihypertensive treatment all the above parameters showed reversal in the respective levels of serum malondialdehyde and antioxidant activity. Antihypertensive medications lower the blood pressure and thereby results in reduced oxidative stress which indicates that oxidative stress is not the cause, but rather a consequence, of hypertension.