En esta investigación se dan a conocer algunos resultados de un estudio longitudinal mixto de crecimiento, observado en niños de 3 escuelas de la Ciudad de México, predominantemente de estatus social medio, los resultados mostraron que la estatura y peso son menores en niñas premenárquicas que en las posmenárquicas, lo que implica que a una mayor madurez sexual existe un incremento de maduración ósea y corporal.Bone age was appreciated in a mixed-longitudinal growth study of 230 girls from age 10 to 15.5 years. In the course of time 988 X-ray films-were obtained and evaluated according to the TW-II method for 20 bones. Our data were correlated with the age at menarche and it was shown that the bone age was higher than the chronological age among the postmenarcheal girls in comparison on with the menarcheal and still lower bone ages were found among the premenarcheal girls. Comparing our results with the british standards (Tanner et al., 1975), even mexican premenarcheal girls resulted to be above the median values for british girls at the same chronological age