The antihypertensive efficacy and tolerability of enalapril (E) and slow-release verapamil (V) were compared in a 2-month double-blind cross-over study in 22 patients with mild to moderate essential hypertension. After 1 month, significantly lower systolic (P less than 0.01) and diastolic (P less than 0.02) blood pressures (BP) were achieved with E, 20 mg d-1, compared with V, 240 mg d-1. After 2 months of treatment, BP reductions were similar after E, 40 mg d-1, and V, 240 mg twice a day. The fall in supine mean BP after 2 months of treatment with V was significantly greater in patients aged greater than or equal to 50 years of age (P = 0.02) (median 18 mmHg) than in patients aged less than 50 years (10 mmHg). E showed similar effectiveness in both age groups. Statistical group analysis of a quality-of-life questionnaire showed no significant differences between the active drugs and the placebo. It is concluded that E and V are equally effective as antihypertensive agents, and that both drugs are well tolerated.