To investigate whether reduction in blood pressure has a beneficial effect on left ventricular diastolic function, we investigated 20 hypertensive patients with evidence of diastolic dysfunction at baseline and at 3 and 6 months after initiation of captopril therapy. Two-dimensional echocardiography was used to determine left ventricular mass index and Doppler ultrasound to assess diastolic function. Fifteen of the 20 patients had a significant reduction in blood pressure at 3 and 6 months and left ventricular mass index remained unchanged during the study period. Despite reduction in blood pressure, no difference in isovolumic relaxation time, early and atrial filling velocities or their ratio was observed. Our results suggest that a direct relationship between blood pressure and left ventricular diastolic function does not exist and that other factors such as alterations in muscle or collagen composition of the left ventricle may be more important in determining abnormal diastolic function in hypertension.