To understand mechanisms of association between hemoglobin and cardiovascular disease (CVD), the relationships between hemoglobin and CVD risk factors were examined in 5115 black and white men and women who participated in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Hemoglobin was higher in men than women, whites than blacks, and smokers than non-smokers (p < 0.001). After adjusting for age, body mass index, current smoking status, and clinical center, hemoglobin correlated with diastolic blood pressure (0.11 < or = r < or = 0.22, p < 0.001) and plasma total cholesterol (0.08 < or = r < or = 0.11, p < 0.01) in all four race-sex groups and with systolic blood pressure in all but black women (0.07 < or = r < or = 0.13, p < 0.05). Among other factors possibly related to CVD risk, only serum albumin and white blood cell count showed significant correlations with hemoglobin in all groups (0.19 < or = r < or = 0.27, 0.07 < or = r < or = 0.18, respectively). These findings suggest that an association of hemoglobin with CVD risk factors may explain the association of hemoglobin with CVD.