OBJECTIVE This trial was designed to evaluate the efficacy and safety of three different classes of antihypertensive agents in elderly women. METHODS The trial had three phases: 4 to 8 weeks of placebo, 6 weeks of titration, and 16 weeks of maintenance. White women between 60 and 80 years old with sitting diastolic blood pressures (DBPs) from 95 through 114 mm Hg treated with placebo were evaluated by history, physical examination, laboratory studies, and quality-of-life interview. After double-blind randomization with low-dose atenolol, enalapril, or isradipine, the dose was increased stepwise and hydrochlorothiazide added as needed to achieve goal DBP (less than 90 mm Hg and greater than 10 mm Hg below baseline). During maintenance, patients not at goal were "stepped up," and patients with uncontrolled DBP at maximum dosage were removed from the study. The pretreatment (baseline) blood pressure of the 315 randomized participants averaged 161/100 mm Hg; 92% had been treated previously for hypertension, 15% had diabetes mellitus, 11% smoked, and 38% consumed alcohol. RESULTS For 245 patients completing the trial, the average decrease in blood pressure during treatment was 18.2/15.6 mm Hg. Antihypertensive efficacy was similar for the monotherapy drug regimens, with 84%, 71%, and 80% of patients receiving atenolol, enalapril, and isradipine, respectively, achieving DBP goal. Of the 70 patients who did not complete the trial, 42 left because of symptoms and 19 because of uncontrolled DBP. No important, unexpected drug-induced changes in symptoms or blood chemistries were noted. Symptom frequency differed little among the three dosage levels, becoming maximal by the second visit at the same dosage level. CONCLUSIONS All three drugs lowered DBP comparably, and none produced alarming effects. Thirteen percent of patients left the study because of symptoms.