OBJECTIVES. Obesity may be a possible explanation for the higher cardiovascular disease mortality in Black women compared with White women. The National Heart, Lung, and Blood Institute Growth and Health Study (NGHS) is designed to assess factors associated with the development of obesity in Black and White preadolescent girls and its effects on major cardiovascular-disease risk factors. METHODS. NGHS is a 5-year cohort study of 2379 girls, aged 9 through 10 years at entry. Anthropometry, blood pressure, and maturation staging are measured annually, and blood lipids biannually. Information on education, income, and family composition is also obtained from parents. RESULTS. At baseline, compared with White girls, Black girls were slightly older, biologically more mature, taller, heavier, and had higher Quetelet Indices, skinfolds, and blood pressures. Black girls had lower triglycerides and higher HDL cholesterol than White girls. Total cholesterol and LDL cholesterol were similar in the two groups. CONCLUSIONS. Baseline descriptive characteristics of the NGHS cohort showed that, in subjects aged 9 and 10 years, racial differences in obesity and blood pressure were already present.