Objectives: To identify ages when adolescents were in sexual maturity stages 2 through 5; to explain the relations between breast (girls), genital (boys), and pubic hair (girls and boys) development between ages 91?2 and 151?2 years; and to evaluate synchrony of pubertal development across characteristics. Design: Annual pubertal assessments. Setting: Ten locations in the United States. Participants: A total of 859 adolescents (427 boys [49.7%] and 432 girls [50.3%]; 737 white [85.8%] and 122 black [14.2%]). Main Outcome Measures: Changes in the 5 stages of breast, genital, and pubic hair development. Results: Girls were in breast maturity stages 2 and 3 earlier than comparable pubic hair stages. Although breast development in girls started earlier than pubic hair development, girls completed breast and pubic hair development at approximately the same age. Black girls were in all stages of breast and pubic hair development earlier than white girls. Boys were in stages 2, 3, 4, and 5 of genital development before the comparable pubic hair stage. In boys, genital development started earlier than pubic hair development, but pubic hair development was completed in less time. Black boys were in genital and pubic hair development about 7 months earlier than white boys. Black and white boys completed genital development in approximately 41?2 years, but black boys took approximately 6 months longer than white boys to complete pubic hair development. At stage 2, for 66.2% of girls, breast development preceded their pubic hair development; for 91.1% of boys, genital development preceded their pubic hair development. Conclusions: The results of this study are useful in understanding normative variation in the timing and change in the development of secondary sexual characteristics at puberty. They will help identify adolescents with atypical changes in sexual maturation and unusual progression of sexual maturation and growth disorders.