This study compared the efficacy and tolerability of eplerenone and enalapril in 499 patients with stage 1 or 2 hypertension who were randomized to receive eplerenone or enalapril for 6 months in a 3-step titration-to-effect study. After 6 months, patients whose diastolic blood pressure (BP) was <90 mm Hg had their dosages down-titrated were followed for an additional 6 months. Diastolic BP was the primary end point. Eplerenone was as effective as enalapril in reducing both systolic BP (eplerenone, -14.5 mm Hg; enalapril, -12.7 mm Hg; p = 0.199) and diastolic BP (eplerenone, -11.2 mm Hg; enalapril, -11.3 mm Hg; p = 0.910) at 6 months. BP reductions at 12 months were also similar between groups (-16.5/-13.3 mm Hg for eplerenone, -14.8/-14.1 mm Hg for enalapril; p = 0.251 and 0.331, respectively). Withdrawal rates for adverse events (eplerenone 7.9%, enalapril 9.3% at 6 months) and treatment failures (eplerenone 23.3%, enalapril 22.8% at 6 months) were also equivalent. Approximately 2/3 of each group had normal BP with monotherapy treatment at 6 months. BP response was independent of renin levels in the eplerenone group, but not in the enalapril group. Both agents reduced albuminuria in patients who had an elevated value at baseline, with significantly greater improvement in patients treated with eplerenone versus enalapril (-61.5% vs -25.7%; p = 0.01). Both agents were similarly well tolerated, and there was no increased incidence of any sexual adverse events in the eplerenone group. Patients taking enalapril had a higher rate of cough. Both agents increased serum potassium levels, but <1% in each group reported adverse events from hyperkalemia. Eplerenone was as effective as enalapril as monotherapy in patients with stage 1 or 2 hypertension, was more effective in reducing albuminuria, and was well tolerated for 12 months.