Abstract: Estimation of amino acid requirements is a complex problem where many factors such as experimental conditions, genetic strain, gender, growth rate, protein quality and level of other dietary nutrients may interfere with the response. Due to the difficulties of using empirical research to resolve these problems, several mathematical growth models have been developed which could be useful for this purpose. Among the models proposed, the OmniPro® II growth model was chosen to evaluate its accuracy to estimate protein and amino acid requirements for broilers under a commercial feeding program. Diets formulated based on levels of protein and amino acids estimated by OmniPro® II were compared with diets based on NRC (1994) recommendations. Significant differences between sexes were observed for all variables evaluated. Broilers fed diets formulated with 100% of OmniPro® II estimations had BW that was similar to those fed diets based on NRC or 110% OmniPro, and were significantly heavier than those fed the 90% OmniPro diets. The feed conversion of male broilers fed diets based on OmniPro recommendations was significantly better than that of chicks fed diets based on NRC recommendations. Females fed with diets according to OmniPro or NRC had the highest dressing percentage, and differed only from those fed the 90% OmniPro diets. These data suggest that nutrient estimations generated by the OmniPro® II support performance equal to or better than that of broilers fed diets based on NRC nutrient recommendations.