In most hypertensive patients, changes in left ventricular systolic and diastolic functions may take place before myocardial hypertrophy occurs. Calcium antagonists, particularly the dihydropyridines, can effectively prevent and treat cardiac complications of hypertension. Felodipine, a dihydropyridine calcium antagonist with high vascular selectivity, appears to act on vascular myogenic tone by affecting the voltage-dependent calcium channels. In the present study, the left ventricular function of 15 patients with mild-to-moderate hypertension (mean age, 57.8 years) was monitored using radionuclide angiography. After a 4-week washout period and then after a 4-week treatment period with extended-release felodipine (10 mg/day in a single daily dose), the patients underwent 24-hour ambulatory blood pressure monitoring and radionuclide angiography at rest and after exercise (75 W for women and 100 W for men). Felodipine significantly reduced systolic, diastolic, and mean blood pressures without significantly affecting heart rate. Ventricular function also significantly improved after felodipine treatment, particularly during diastole. In its extended-release formulation, felodipine significantly reduces patients' blood pressure and considerably improves ventricular function both at rest and under stress. Its potential as an efficacious long-term treatment for hypertension and its associated complications is clearly demonstrated.