Hypertension and progressive deterioration in renal function are commonly seen in heart transplant recipients treated for the long term with cyclosporine. Because angiotensin converting enzyme inhibitors have been associated with amelioration of renal dysfunction in some patients with hypertension and preexisting mild-moderate kidney failure, we treated nine hypertensive recipients of orthotopic heart transplants with enalapril (11 +/- 2 mg/day) and furosemide (62 +/- 15 mg/day) for 23 +/- 4 months. Most of the enalapril dose was given at bedtime, which minimized nocturnal and early morning hypertension. In addition to controlling blood pressure (154 +/- 6/100 +/- 2 mm Hg before enalapril vs 120 +/- 5/81 +/- 2 mm Hg currently; p less than 0.001 for both systolic and diastolic blood pressures by paired t test), there has been no increase in serum creatinine level over 684 +/- 102 days of follow-up (1.88 +/- 0.20 mg/dl before enalapril vs 1.81 +/- 0.17 mg/dl currently; p greater than 0.70). This is unlikely to be caused by the reduction in daily cyclosporine dose (492 +/- 60 mg/day before enalapril to 305 +/- 47 mg/day currently) because there were no significant changes in mean blood cyclosporine level (which has been maintained between 100 and 500 ng/ml). Treatment of hypertension with enalapril and a diuretic after heart transplantation may help prevent or delay the impairment of renal function often seen during prolonged cyclosporine therapy.