The long-term antihypertensive effects of enalapril were assessed for a period of up to 1 year in 44 elderly patients with mild-to-moderate essential hypertension. Following a 2-week placebo period, patients who were assigned to enalapril were followed for 6 weeks in a randomized clinical trial. In patients who benefited from enalapril, treatment was continued and subjects were followed for up to 1 year. Supine and standing systolic and diastolic blood pressures were significantly reduced throughout the 1-year period compared with baseline. The dosage of enalapril was increased from 10 to 20 mg daily in 12 patients; 8 required additional antihypertensive agents. Enalapril is effective in the long-term treatment of hypertension; no loss of antihypertensive effect occurs.