The study involved 113 patients over age 50 years with mild to moderate essential hypertension, randomly assigned to treatment with enalapril (n = 54) or sustained-release verapamil (n = 59). During an eight-week titration period, doses were adjusted to achieve supine diastolic blood pressures (DBP) below 90 mmHg; patients were then given maintenance doses for eight weeks. Mean blood pressures were reduced significantly from 147.7/93.9 mmHg at baseline to 137.7/84.5 mmHg at the end of the maintenance period in the enalapril group and from 155.1/95.1 to 142.4/86.2 mmHg in the verapamil group. In the patients who completed treatment, the mean daily doses required to maintain DBP below 90 mmHg were 9.6 mg of enalapril and 244.9 mg of verapamil. There were 11 treatment failures in the enalapril group and 22 in the verapamil group: eight of the enalapril and 17 of the verapamil patients did not attain goal blood pressures and three and five were withdrawn because of side effects. It is concluded that both enalapril and sustained-release verapamil were generally effective and well tolerated in the treatment of mild to moderate hypertension in the middle-aged and older patients.