In a double-blind randomised parallel group trial a new angiotensin-converting enzyme (ACE) inhibitor, Spirapril, was compared to nitrendipine in 266 patients with hypertension (diastolic blood pressure 95 to 119mm Hg). Blood pressure was measured 24 hours after administration, and dose titration was performed every fourth week to achieve a diastolic blood pressure ⩽ 90mm Hg. After 4 weeks’ monotherapy with either nitrendipine 20mg once daily or Spirapril 12mg once daily, the dose was increased to 40mg once daily and 24mg once daily, respectively, if goal blood pressure had not been achieved. After 8 weeks of monotherapy hydrochlorothiazide 12.5mg once daily could be added.