The antihypertensive effect of celiprolol, a selective beta-adrenoceptor blocker with ancillary partial beta 2-agonist, vasodilator, and bronchosparing properties, has been evaluated in open and placebo-controlled trials. Celiprolol (200-600 mg once daily) has been reported to reduce blood pressure significantly in 60-80% of patients with side effects which are mild and low in frequency. The antihypertensive efficacy of celiprolol has been found comparable with that of propranolol, atenolol, metoprolol and nadolol, but celiprolol does not cause the same degree of bradycardia as these other drugs. By means of ambulatory blood pressure monitoring we have demonstrated that celiprolol, administered to 10 essential hypertensive patients (aged 20-64 years) as a single daily dose (200-400 mg), can induce a significant and sustained reduction in 24-h systolic and diastolic blood pressure, with no effects on 24-h heart rate. Similar results have been obtained in elderly patients (aged 65-74 years) responsive to this drug. Both in young and elderly patients treatment was well tolerated. Available evidence therefore suggests that celiprolol is an effective and safe antihypertensive drug, the favorable ancillary properties of which are likely to make its administration feasible in a broad range of patients.