We have conducted a multicentre study in patients with mild to moderate hypertension. Lisinopril monotherapy, 10, 20, or 40 mg once daily (n=35), was compared with captopril monotherapy, 25, 50, or 100 mg twice daily (n=35). Blood pressure assessments were conducted using both office and 24-hour ambulatory blood pressure monitoring. Area under the curve analysis of ambulatory blood pressure reductions demonstrated significant differences between once-daily lisinopril and twice-daily captopril, with lisinopril producing the most significant reduction in pressure. These therapeutic results reflect the clinical-pharmacological profile of these two angiotensin-converting enzyme inhibitors and provide important clinical implications.