The orally active angiotensin-converting enzyme inhibitor captopril was administered for up to 11 weeks to three patients with progressive systemic sclerosis presenting with hypertension and plasma creatinine levels of 3.1, 7.2 and 10.4 mg/100 ml. Only one patient had malignant phase hypertension. In this patient a diuretic had to be added to captopril in order to keep blood pressure under control. Despite sustained blood pressure control during captopril administration, renal function deteriorated and hemodialysis treatment had to be started in all patients. Up to that time no substantial improvement in skin lesions was observed. During the period of dialysis, blood pressure was normal in all patients even though administration of captopril was discontinued. All three patients died of respiratory failure while on chronic hemodialysis for 3 to 4 weeks. These observations confirm that angiotensin-converting enzyme inhibition may be helpful in controlling blood pressure of patients with scleroderma. However, in contrast to some earlier reports, they also indicate that converting enzyme inhibition does not always prevent the multivisceral vascular lesions of scleroderma.