The safety and efficacy of once-daily lisinopril was assessed in an 8-week open-label study of 24 elderly patients with mild to moderate hypertension. Following withdrawal of all previous antihypertensive treatment, including diuretics, lisinopril treatment was started at a dose of 5 mg, increasing to a maximum of 40 mg once daily as required. Treatment provided effective 24-h BP control in all patients, most of whom required a daily dose of 20-40 mg, and cardiothoracic index decreased significantly, indicating a favourable effect on left ventricular volumes. There were no significant ECG alterations and no major side effects occurred. It is concluded that lisinopril 5 mg is a safe starting dose for elderly patients who are not on diuretics, and that once-daily lisinopril monotherapy reduces BP safety without affecting heart rate.