In a half-year open clinical study the authors investigated the antihypertensive action of enalapril--an inhibitor of the angiotensin converting enzyme--and its action on renal functions in a group of 11 patients with nephrogenic hypertension. In seven patients monotherapy, using a mean dose of 12 mg, was sufficiently effective. In the remaining four patients treatment was combined with diuretics. It was revealed: that: 1. a significant drop of systolic and diastolic pressure occurred with a concurrent decline of the total peripheral vascular resistance, 2. a slight (statistically not significant) reduction of the glomerular filtration as well as quantitative proteinuria with a decline of glomerular hypertension. 3. In this group of patients without left ventricular hypertrophy no signs of regression of its mass were present. 4. Even in patients with nephrogenic disease no negative effect on the lipid, carbohydrate and purine metabolism was observed. The subjective tolerance of the preparation was very satisfactory.