Captopril, an orally active angiotensin I-converting inhibitor, is an effective drug in the treatment of hypertension in adults and children. The use in newborn infants has been, nevertheless, short. We report five cases of hypertension in newborn infants poorly responsive to large doses of other potent antihypertensive agents: furosemide, propanolol and hydralazine. We have got a reduction in mean blood pressure in three cases, with doses of 0.1-0.2 mg/kg/day for a time lesser than a month. Another patient had a reduction with high doses (5 mg/kg), showing increase in mean serum urea, creatinin, potassium and phosphorus levels. This effect disappeared after captopril was discontinued. We suggest the use of captopril in hypertension non-responsive to other antihypertensive agents, mainly in those of renovascular cause.