Objectives. Although differences in obesity between Blacks and Whites are well documented in adult women, less information is available on potential correlates of these differences, especially in young adults. Methods. The association between behavioral and demographic factors and body size was assessed in 2801 Black and White women aged 18 to 30 years. Results. Black women had significantly higher age-adjusted mean body mass index and subscapular skinfold thickness than did White women. Obesity had different associations with age and education across racial groups. A positive relationship between age and obesity was seen in Black women but not in White women, whereas a negative association between education and body size was noted only in White women. Potential contributing factors to the increased prevalence of obesity in Black women include a more sedentary lifestyle, higher energy intake, earlier menarche, and earlier age at first childbirth. Conclusions. The difference in obesity across race could not be explained completely by these factors, since within virtually all strata, Black women had higher body mass indexes. Further investigation is needed to develop interventional strategies to prevent or reduce excess levels of obesity in Black women.