Although diuretics are recommended for the treatment of hypertension, decreased diuretic use and increased calcium antagonist use necessitate a comparison of the efficacy of these drugs in preventing cardiovascular events. Patients >/=60 years of age with systolic blood pressure of 160 to 220 mm Hg and diastolic blood pressure <115 mm Hg were enrolled. Patients were randomly assigned to 20 mg of sustained-release nicardipine hydrochloride twice daily or 2 mg of trichlormethiazide once daily by the double-dummy method and followed up for 5 years. A total of 414 patients were analyzed: 204 in the nicardipine group and 210 in the diuretic group. Blood pressure at entry was 172/94 mm Hg and 173/93 mm Hg, respectively, and decreased to 147/81 mm Hg and 147/79 mm Hg, respectively. Cardiovascular morbidity rates per 1000 persons per year were similar in the nicardipine and diuretic groups (27.8 and 26.8, respectively; P=0.923). The sex- and age-adjusted risk ratio for the nicardipine group was 0.973 (95% confidence interval, 0.514 to 1.839, P=0.932). The calcium antagonist and diuretic groups had a similarly decreased rate of cardiovascular events.