The goal of this study was to investigate the relationship between hematocrit (Hct) and left ventricular mass index (LVMI) and LV hypertrophy (LVH) in subjects without known hypertension or cardiovascular disease in the Framingham Heart study.Anemia may be an independent risk factor for cardiovascular disease in the general population. One potential explanation for this finding could be an association between Hct with LVMI or LVH.Linear and logistic regression analyses were used to evaluate the association between Hct with LVMI and LVH. All analyses were stratified by gender and further according to menopausal status in women.There were 1,376 men and 1,769 women who met the inclusion criteria. The mean Hct and LVMI were 46.5% and 41.9%, and 127.3 and 95.8 g/m, respectively, in men and women. After adjustment for confounders, each 3% lower Hct was associated with a 2.6 g/m higher mean LVMI in men, and a 1.8 g/m higher mean LVMI in postmenopausal women (p < 0.05). There was a significant quadratic relationship between Hct and LVMI in premenopausal women (p < 0.01). Subjects in the lowest quartile of Hct (compared with the rest of the sample) had an adjusted odds ratio of LVH of 2.0 (95% confidence interval [CI] 1.3 to 3.0) in men and 1.4 (95% CI 0.8 to 2.4) in postmenopausal women.In a sample without known hypertension or cardiovascular disease, a lower Hct is associated with echocardiographically determined LVH in men and a small but significantly higher LVMI in men and postmenopausal women. The clinical importance of these findings remains unknown.