Data from the United States Health Examination Survey, Cycle III, were used to describe the relationships among secondary sexual characteristics, bone age, and body mass index of girls aged 12 to 17 years. The survey examined a sample of girls representative of the American population with respect to race, age, geographic region, and socioeconomic status. Tanner stages for breast and pubic hair development correlated closely. There was also a close relationship between Tanner rankings of sexual maturity and both bone age and body mass index (weight/height). Socioeconomic status was not related to sexual development, but there were significant racial and geographic differences in the age of development of secondary sexual characteristics. The Health Examination Survey data provide standards of sexual and physiologic growth for U.S. girls.