The level of arterial pressure is not the sole determinant of cardiac adaptation to hypertension. In order to identify other factors (such as preload as well as neuro-humoral factors) we categorized by M-mode echocardiography, 192 never treated patients with mild to moderate hypertension of short duration, according to values of end-diastolic relative wall thickness (RWT) and left ventricular mass index (LVMI). Mitral regurgitation was excluded in all patients by Doppler echocardiography. Among hypertensive patients, LVMI and RWT were normal in 43% (group 1), whereas 20% had increase RWT with normal LVMI "concentric remodeling" (group 2), 24% had concentric hypertrophy (increase both LVMI and RWT) (group 3) and 13% had increased LVMI with normal RWT (eccentric hypertrophy) (group 4). Results presented as means +/- SD. [table: see text] In addition the acute response after ACE-inhibition (captopril 50 mg) of mean arterial pressure was significantly attenuated in group 4 when compared with group 1. These results suggest that the effect of arterial pressure on the heart may be modulated by volume overload (low PRA and high CI) in hypertensive patients with eccentric LV hypertrophy with normal LV function.