Beef cattle production represents an important source for development of Brazilian agribusiness. The reproductive performance of the herds needs to be evaluated according to traits associated directly with the productive efficiency of the herds and as a result economic gain by decreasing beef production cycles. The age at first calving (AFC) is used in genetic evaluation of the Nelore cattle as indicator of the sexual precocity in females. The gestation length (GL) in the Nelore cattle genetic improvement program is assessed by days less than length of gestation, reflecting in favorable effect on reproductive and economic performance, because the weight of the calf at birth can be optimal, reducing the number of difficult calving by reducing birth weight, and increase of the reproductive efficiency of the cow. The present investigation aims to provide tools for the selection of Nelore breed animals participating in a cattle breeding program and obtain genetic associations for reprodutive traits.