Introduction: The assessment of biological maturation is considered essential to health, because it can be used directly for the clinical interpretation of endocrine, growth status and quality of life. Objective: To validate the proposed technique by Mirwald et al (2002) to assess the maturity and develop an equation to calculate the cross peak growth rate of children and adolescents from public schools in the urban region of Campinas, SP, Brazil. Methods: We selected 914 stratified probability so boys and 839 girls, which correspond to 30% of a total of 5931 school children 8-16 years of both sexes of an urban region of Campinas, SP, Brazil. We evaluated the decimal age and anthropometric variables of height, weight and sitting height. Interrelationships were conducted weight / height and length was determined by calculating the lower the difference between the sitting height and stature. To validate the equation criterion (Mirwald et.al 2002) cross-validation was used both internally and externally. Results: We observed high correlations between age and anthropometric variables in both boys (r = 0.56 to 0.96) and in girls (r = 0.57 to 0.98). The internal and external validation no significant difference (p> 0.05) and acceptable agreement was observed between the test and the equations developed for children of both sexes to a 95% CI. Conclusions: We conclude that Mirwald et al (2002) regression equations are validated and can be applied to schools in the urban region of Campinas, SP (Brazil). The equations developed in the study are an alternative toassess somatic maturation across.