Scleroderma is a disease of unknown cause characterized by interstitial fibrosis and vascular lesions in many organ systems. Renal failure, often associated with malignant hypertension, may ensue as a life-threatening component of this disorder. Activation of the renin-angiotensin-aldosterone system has been hypothesized as a cause of this complication. Captopril has been used in 23 patients with this condition. Of this group, 20 (87%) responded favorably with a decrease of the supine diastolic BP to less than 90 mm Hg and a reduction in the serum creatinine level in 14 patients. During long-term therapy (median, 29 months), 11 of the 23 patients continued to have a good clinical response while receiving captopril. Six patients died and six patients were alive after captopril therapy was discontinued. These data suggest that captopril is beneficial in the treatment of scleroderma renal crisis.