To evaluate its antihypertensive efficacy and safety in elderly hypertensive patients, the angiotensin-converting enzyme inhibitor cilazapril was compared to the calcium antagonist nitrendipine in a randomized, double-blind, multicenter trial with 114 subjects (mean age, 68 years; diastolic blood pressure, 90–115 mm Hg; systolic blood pressure, 140–220 mm Hg). After a 1-month placebo washout period, patients received either cilazapril, 2.5–5 mg, or nitrendipine, 10–20 mg, once daily for 12 weeks. After 4 weeks, the dose was doubled in non-responders. The higher dosage level was administered to 42% of patients in the cilazapril-treated group and to 47% in the nitrendipine-treated group. Blood pressure was measured before (at 60 min and 30 min, and just prior to administration) and at 60. 90, and 120 min after drug administration. Both cilazapril and nitrendipine significantly (p < 0.01) reduced systolic and diastolic blood pressure. The decrease in systolic blood pressure measured at trough was significantly greater with cilazapril than with nitrendipine (-17 vs. −12 mm Hg, p < 0.05), but the effect of the two drugs on diastolic blood pressure was similar (-11 mm Hg). Tolerability was assessed by means of adverse events, laboratory assessments, psychometric tests, and questionnaires on mood states and sleep. Adverse events were reported by 99? of patients in the cilazapril group and by 21% of patients in the nitrendipine group (p < 0.05). Laboratory test results and profiles for mood, sleep, memory, and attention were not affected by either treatment. Thus, cilazapril and nitrendipine both appear to be effective and well tolerated antihypertensive agents in the elderly patient.