For unclear reasons, anemia is more common in American blacks than whites. The authors evaluated anemia prevalence (using World Health Organization criteria) among 19,836 blacks and whites recruited in 2003-2007 for the REasons for Geographic And Racial Differences in Stroke Renal Ancillary study and characterized anemia by 3 anemia-associated conditions (chronic kidney disease, inflammation, and microcytosis). They used multivariable models to assess potential causes of race differences in anemia. Anemia was 3.3-fold more common in blacks than whites, with little attenuation after adjusting for demographic variables, socioeconomic factors, and comorbid conditions. Increasing age, residence in the US southeast, lower income, vascular disease, diabetes, hypertension, and never smoking were associated with anemia. Age, diabetes, and vascular disease were stronger correlates of anemia among whites than blacks (P < 0.05). Among those with anemia, chronic kidney disease was less common among blacks than whites (22% vs. 34%), whereas inflammation (18% vs. 14%) and microcytosis (22% vs. 11%) were more common. In this large, geographically diverse cohort, anemia was 3-fold more common in blacks than whites with different characteristics and correlates. Race differences in anemia prevalence were not explained by the factors studied. Future research into the causes and consequences of anemia in different racial groups is needed. © The Author 2008. Published by the Johns Hopkins Bloomberg School of Public Health. All rights reserved.