One hundred eighteen patients, aged between 65 and 87 years with mild-to-moderate hypertension were given placebo or isradipine (1.25 to 5 mg twice daily, or 2.5 to 10 mg once daily) following a three-week placebo period to evaluate its safety and efficacy in elderly patients. Dosage step-up was at three-week intervals. Blood pressure measurements were taken immediately before the morning dose (12 to 24 hours after the previous dose). At the end of the study, both supine and standing diastolic blood pressures were significantly lower with isradipine than with placebo. A 10-mm Hg reduction in supine diastolic blood pressure was achieved with once-daily isradipine in 65 percent and with twice-daily isradipine in 52 percent of patients, indicating sustained blood pressure control over the dose interval (12 to 24 hours). Adverse events were usually mild, transient, and typical for vasodilators. Isradipine did not produce more laboratory, clinical, or electrocardiographic abnormalities than did placebo. In conclusion, isradipine either once or twice daily at doses between 2.5 and 10 mg is an effective and well-tolerated treatment for mild-to-moderate hypertension in elderly patients.