The National Growth and Health Study, NGHS, was an epidemiologic study of 2,379 black and white girls, ages 9-10 years at entry, who were followed annually. The ancillary study had the potential for identifying those genes involved in determining Black/white differences in lipid metabolism and obesity. This was an exciting area in which there was virtually no available information. Finally, the study permitted an examination of the effects of gene variation on changes in quantitative levels of blood lipids as well as in body fat during different stages of pubescence since the NGHS protocol included annual anthropometric and maturation assessments and biannual blood lipid determinations along with extensive environmental measures which included dietary, household, and psychosocial information. The study was unique because of the rare opportunity to do genetic analyses in a large cohort of two ethnic groups of children on whom a very rich data base was available.