The effect of antihypertensive therapy on regression of left ventricular hypertrophy and left ventricular diastolic function was investigated in 25 hypertensive patients for up to 18 months after initiation of treatment. Left ventricular mass index was calculated by two-dimensional echocardiography and left ventricular diastolic function assessed by transmitral pulsed doppler ultrasound. Significant reduction in left ventricular mass index was observed after 9 months of treatment. Only 13 patients had a reduction in mass greater than the intraobserver variability of the technique. There was no change in doppler indices of left ventricular diastolic function. In 7 patients who were studied for a further 9 months after regression had occurred there was still no appreciable difference in left ventricular diastolic function. These findings indicate that there is no direct relation between left ventricular mass and abnormal left ventricular diastolic function.