Changes in hemodynamic variables regulating systolic function were examined by M-mode echocardiography in 14 patients with long-duration primary uncomplicated hypertension treated with nitrendipine once daily (20mg). At the end of treatment (8th week) blood pressure and peripheral resistance were greatly reduced (p<0.0001), while the indices of cardiac function (ejection fraction and cardiac index) showed significant increases (p<0.01). The variations in ejection fraction were analyzed by multiple linear regression and were mainly influenced by the decrease in end-systolic stress (contribution: 60%). At baseline, despite no radiographic or clinical signs of heart failure, 6 of the studied patients showed impaired systolic function, likely due to the strength of other variables (age, risk factors); in those patients, systolic function was clearly enhanced at the end of treatment, while no change was found in patients with initial normal pump function. Changes in cardiac output were due toasignificant increase in heart rate in patients with normal pump function and to improved stroke volume in the others. Left ventricular mass index was slightly reduced (p<0.005), primarily because of the reduction in end-diastolic volume (p<0.01). When analyzed by the 2 subgroups (with or without impaired systolic function), the left ventricular mass index appeared to be significantly reduced only in those patients with normal basal pump function. This difference was most likely due to the different effects of treatment on enddiastolic volume.