Arterial hypertension may be associated with altered left ventricular filling dynamics. The specific goal of this study was to evaluate whether short-term administration of the ACE inhibitor lisinopril in hypertensive patients with an altered diastolic pattern induced an improvement of left ventricular dynamics, assessed by the echocardio-Doppler technique, independently of effects on left ventricular mass. In a double-blind cross-over study 39 essential hypertensive patients with a ratio of peak early to peak atrial velocity (E/A) < 1 were randomized, after a run-in period of 2 weeks without any antihypertensive treatment, to receive lisinopril (20 mg once a day) and placebo for 4 weeks, respectively. At the end of both the run-in and the treatment periods, blood pressure and heart rate were measured and an echocardio-Doppler examination was carried out. The echocardio-Doppler evaluation was performed both at rest and at the peak of a hand-grip test (3 min at 30% of maximal strength). Left ventricular dimensions were obtained from two-dimensionally guided M-mode tracings using the criteria of the American Society of Echocardiography. Left ventricular peak filling rates and filling rate integrals were measured by a pulsed Doppler technique. Lisinopril caused a significant reduction in systolic and diastolic blood pressure at rest (-13/-9 mmHg vs baseline values, p < 0.05; -6/-4 mmHg vs placebo values, p < 0.05) and during isometric exercise (-17/-9 mmHg vs baseline period, p < 0.05; -6/-5 mmHg vs placebo, p < 0.05). Lisinopril did not induce any significant change in left ventricular structure and systolic function. All the left ventricular filling parameters considered (E velocity, A velocity, E/A ratio) both at rest and during isometric exercise did not significantly differ after lisinopril treatment when compared to those obtained in basal conditions and after placebo administration. This double-blind cross-over study demonstrates that short-term afterload reduction induced by lisinopril does not modify altered diastolic dynamics in hypertensive patients. Diastolic dysfunction of the left ventricle is a complex process influenced by a number of functional and structural factors and apparently cannot be significantly improved by short-term blood pressure reduction by antihypertensive therapy.