The effect of enalapril and low prednisone doses on the urinary protein electrophoretic pattern was studied in 13 pediatric patients with glomerular diseases and steroid-resistant nephrotic syndrome. Enalapril was administered at doses of 0.2-0.6 mg/kg per day for 24-84 months, and prednisone was introduced 2 months later in 11 patients at doses of 30 mg/m2 on alternate days. The urine protein electrophoretic pattern showed a reduction of 80% and 70% in the total protein and albumin, respectively, after enalapril. Total urinary protein decreased from 5.46 to 1.1 g/m2 per day (P<0.001). A marked change from a pattern of non-selective urinary protein loss to an albumin-selective proteinuria was observed. Mean total plasma proteins increased from 4.7 to 5.43 g/dl (P<0.001). Four patients became free of proteinuria 24 months after enalapril was started, but only 2 remained free of proteinuria at 48 months of follow-up. The other 11 patients had persistent albuminuria of between 0.5 and 2.6 g/m2 per day with a selective urinary electrophoretic pattern. No additional decrease was observed after steroids were introduced. A clinical improvement in edema was observed in all children. Three patients developed transient acute renal failure, during the course of an infectious disease; 2 developed peritonitis and 1 pneumopathy. In these patients withdrawal of enalapril was necessary until a complete recovery of renal function was observed. Four patients were hypertensive on admission, achieving normal blood pressure 1 month after enalapril was started. No episodes of systemic arterial hypotension were seen. Creatinine clearance and serum potassium showed no statistically significant change.