OBJECTIVES: To determine the current prevalence and mean ages of onset of pubertal characteristics in healthy urban Chinese girls. METHODS: A cross-sectional study of sexual maturation of healthy Chinese girls was conducted in 9 representative cities of the eastern, western, southern, and northern parts and central region of China between 2003 and 2005. At examination, stages of breast and pubic hair development were rated on girls 3 through 19.83 years of age, and height and weight were also recorded. Data on menses were collected by the status quo method. Probit analysis was used to calculate the median age and 95% confidence interval (CI) for onset of breast and pubic hair development and menarche. RESULTS: Data were analyzed for 20 654 apparently healthy girls. At age 8 years, 19.57% of these girls had evidence of breast development. The median ages of onset of Tanner stages 2 and 3 for breast development were 9.20 (95% CI: 9.06-9.32) years and 10.37 (95% CI: 10.28-10.45) years, respectively. The median ages of onset of Tanner stages 2 and 3 for pubic hair development were 11.16 (95% CI: 11.03-11.29) years and 12.40 (95% CI: 12.25-12.55) years, respectively. Menses occurred at 12.27 years (95% CI: 12.16-12.39). CONCLUSIONS: These data suggest that urban Chinese girls are actually experiencing earlier breast development than currently used norms. The up-to-date reference for normal pubertal development in urban Chinese girls needs to be established for the purpose of determining precocious puberty or pubertal delay. Pediatrics 2009; 124: e269-e277