Background: Imidapril is a new angiotensin-converting enzyme inhibitor that has been shown to have potent antihypertensive efficacy in short-term, double-blind studies. Objective: The goal of this dose-finding study was to examine the long-term safety and efficacy of imidapril in the treatment of mild to moderate hypertension. Methods: Patients aged 18 to 80 years with a sitting diastolic blood pressure (DBP) 95 to 115 mm Hg after 2 weeks of placebo run-in were treated with imidapril 5 mg/d, which was titrated at 4-week intervals through 10 and 20 mg/d for 52 weeks. If blood pressure remained uncontrolled (DBP >90 mm Hg), furosemide 20 mg was added. Results: In the intent-to-treat population (n = 354), there was a sustained and significant reduction in mean (+/-SD) sitting DBP from 102.3 +/- 4.5 to 87.9 +/- 7.9 mm Hg at the final visit (P = 0.001). Eighty-five percent of patients were classified as responders (sitting DBP less than or equal to 90 mm Hg or a reduction of greater than or equal to 10 mm Hg). The most frequent adverse events were cough (13%), headache (9%), and bronchitis (7%). Conclusions: In this study, imidapril was a well-tolerated and effective longterm antihypertensive agent, with the 5-mg dose being clinically effective in the greatest proportion of patients (38% [133/354]) and similar proportions requiring 10 mg, 20 mg, or 20 mg plus furosemide (25%, 19%, and 19%, respectively).