Although several studies indicate that there are gender differences in left ventricular (LV) systolic function, it remains unclear whether similar differences exist with regard to diastolic function. Accordingly, Doppler echocardiograms were analyzed in 515 male and 839 female, mostly treated (95%) hypertensive participants enrolled in the Hypertension Genetic Epidemiology Network (HyperGEN) study with no evidence of abnormal wall motion or significant valvular heart disease. There was no difference in age between genders, but after adjusting for age and race, men had lower body mass indexes (29.8 ± 5.2 vs 32.3 ± 7.6 kg/m²) and heart rates (67 ± 12 vs 69 ± 11 beats/min) and higher systolic and diastolic blood pressures (BP) than women (134 ± 20 vs 130 ± 21 and 80 ± 11 vs 72 ± 11 mm Hg, all p <0.001). LV mass/height^2.7 was slightly greater in women than in men (43 ± 10 vs 42 ± 9 g/m^2.7, p <0.05). After adjusting for age, race, systolic BP, body mass index, heart rate, and LV hypertrophy, both mitral E-wave (70 ± 18 vs 77 ± 19) and A-wave (74 ± 15 vs 79 ± 17, both p <0.001) velocities were lower in men than in women, but the mitral E/A ratio and atrial filling fraction were nearly identical in both genders. Deceleration time (221 ± 55 vs 214 ± 46 cm/s, p = 0.018) and isovolumic relaxation time (IVRT) were longer in men than in women (85 ± 18 vs 81 ± 17 cm/s, p <0.001). Prolonged IVRT was present in more men than women (14% vs 7%, p <0.05). In analyses of covariance, adjusting for age, race, systolic BP, body mass index, heart rate, and medications, male gender remained related to prolonged deceleration time and IVRT. Thus, in this population-based sample of hypertensive adults, men had evidence of slower early diastolic LV filling than women. This gender difference in diastolic function may provide insight into gender differences in congestive heart failure and other specific cardiovascular diseases.