Our aim was to assess the differential effect of waist circumference on left-ventricular (LV) structural and functional alterations, in hypertensive males and females. One thousand seven hundred and eighty nine consecutive, nondiabetic, essential hypertensives (aged 55.8 +/- 13.5 years, 966 females), included in the 3H Study, an ongoing registry of hypertension-related-target-organ damage, were classified to obese and nonobese groups according to Adult Treatment Panel III criteria. All participants underwent complete echocardiographic study including LV diastolic function evaluation by means of conventional and tissue Doppler imaging (TDI) methods, averaging early and late diastolic mitral annular peak velocities (Em, Am, Em/Am) from four separate sites of measurement. Hypertensive obese women compared with nonobese exhibited significantly greater LV mass index and prevalence of LV hypertrophy (by 5.5 g/m(2), P = 0.003, and 8.8%, P = 0.005, respectively), while such differences were not present among men. Obese women compared to nonobese ones were accompanied by lower transmitral E/A (by 0.08, P < 0.001), TDI-derived Em/Am (by 0.12, P < 0.001), and higher E/Em ratio (by 0.8, P = 0.016). In contrast, hypertensive obese men compared to nonobese ones exhibited lower E and Em (by 0.04 m/s and 0.6 cm/s, both P < 0.05). A significant interaction between sex and abdominal obesity was observed only regarding TDI-derived Am and Em/Am. Furthermore, waist circumference was a predictor of E/A (beta = -0.097, P = 0.002) and Em/Am (beta = -0.116, P = 0.001), independently of body size, in females but not in males. The adverse effect of abdominal obesity on LV alterations is more pronounced among female hypertensives, suggesting that routine measurement of waist circumference provides additional information on cardiac phenotype especially in women.