Data from population-based studies indicate that men have a higher incidence and worse prognoses of congestive heart failure than women. Echocardiography was used to compare left ventricular (LV) myocardial and chamber contractility between 490 male and 861 female American Indian participants in the second Strong Heart Study examination. After adjusting for fat-free mass, baseline hypertension, diabetes mellitus, coronary heart disease, and alcohol consumption, LV ejection fractions were higher in women than men (66 +/- 8% vs 63 +/- 9%, p = 0.002), as were stress-corrected mid-wall shortening (106 +/- 13% vs 104+/-15%, p = 0.006) and the circumferential end-systolic stress/end-systolic volume index (7.1 x 10(4) +/- 1.9 x 10(4) vs 6.5 x 10(4) +/- 2.1 x 10(4) kdyne/cm3, all p values <0.001). LV ejection fractions were less than the predefined partition value in 4.7% of women and in 16.7% of men (odds ratio 0.25, 95% confidence interval 0.18 to 0.34, p <0.001). Stress-corrected mid-wall shortening was less than the predetermined lower limit of normal in 2.9% of women and in 6.2% of men (odds ratio 0.45, 95% confidence interval 0.29 to 0.70, p <0.001). There was no significant gender difference in supranormal function by either measure of LV systolic function. Estimated mean independent effects of female gender were a 3% greater ejection fraction, 2.7% greater stress-corrected mid-wall shortening, and a 0.4 x 10(4) kdyne/cm3 greater circumferential end-systolic stress/end-systolic volume index. In conclusion, in a population-based sample aged 45 to 74 years, women had greater LV myocardial and chamber function than men. Gender-specific partition values for measures of LV systolic function may be necessary to detect abnormal contractility in clinical and epidemiologic studies.