The effects of two antihypertensive agents, nifedipine (N) and captopril (C), on left ventricular (LV) mass and volume were studied in 16 patients with essential hypertension (8 treated with N and 8 with C for 6 months) by means of a complete M-mode echocardiogram monitored by two-dimensional echocardiography. Both N and C induced a significant reduction in end-diastolic, but not systolic, posterior wall and septum thickness and an increase in end-diastolic volume, but not in end-systolic volume. A significant increase in the contribution of rapid filling together with a simultaneous reduction in the contribution of atrial systole to end diastolic volume were also observed. The reduction in LV wall thickness and mass after both C and N might be attributed to an improvement in diastolic function and to a reduction in wall tension, rather than to an effective regression of LV hypertrophy.