Objective:We estimated pubertal development of 7,493 normal Iranian girls aged 6 to 20 years in a cross-sectional study. Methods:Pubertal stages were assessed according to Tanner. The mean ages to achieve secondary sexual characteristics as well as the mean age at menarche were estimated. Weight and height were measured and body mass index (BMI) was calculated. Reference curves for different breast stages and menarche were constructed. The percentiles for attaining each stage were compared to data proposed by Tanner. Findings: The mean age at breast bud stage (B2) was 10.10, pubic hair stage (P2) was 9.83, and menarche age was 12.55 years. The anthropometric variables were interpreted in different maturity stages. The mean age at attainment of puberty was compared with those of other populations. Conclusion:Not only the onset of puberty in Iranian girls but also the duration of puberty is similar to data from most other countries. A lower age limit for the definition of precocious puberty than the traditional 8 years is documented for Iranian girls. However, it should be noted that considering the rate of evolution of pubertal findings is more important than the age of their appearance.