Five patients (median age 63 years) with severe crescentic glomerulonephritis had acute renal failure (median plasma creatinine 930, range 690-1390). Following induction of immunosuppressive treatment all patients achieved recovery of adequate renal function (median creatinine 440, range 290-570 mumol/l). After 3-6 months of continuous remission, all patients, despite stable renal function developed increasing proteinuria (median 4.4 g/24 h, range 3.2-6.1), and enalapril (5-20 mg per day) was substituted or introduced as antihypertensive therapy. Immunosuppression was not altered. After 1 year, renal function remained stable in four patients and plasma creatinine increased initially in one patient before becoming stable: proteinuria was reduced substantially in all patients to a median of 0.8 g/24 h, range 0.2-1.3). Patients with severe crescentic glomerulonephritis may develop persistent or increasing proteinuria despite successful treatment of acute disease. We have used enalapril to reduce proteinuria and maintain function in such patients.