Ramipril, a once-a-day angiotensin-converting enzyme inhibitor, was studied in the treatment of mild-to-moderate hypertension in 240 patients. A total of 194 patients (111 women and 83 men; mean +/- SD age, 46.0 +/- 11.5 years) were considered assessable for study. After a 2-week placebo washout phase, all patients received ramipril 2.5 mg once daily for 4 weeks. At 4 weeks, blood pressure was evaluated for response to therapy. Responders to 2.5 mg were continued on the same dose; nonresponders received 5 mg once daily for another 4 weeks. Results showed that 91% of patients responded after 8 weeks of therapy, 60% to 2.5 mg and 31% to 5 mg. Ramipril was well tolerated and, because of its long half-life, can be considered a true once-a-day angiotensin-converting enzyme inhibitor for the treatment of patients with mild-to-moderate hypertension.