The association between biochemical polymorphic systems and early sexual maturity was assessed subjecting 16 animals (from 17 to 36 months old) to eletrophoretic studies, searching for transferrin and albumin polymorphisms. Two albumin alleles, AlbA (AlbF) and AlbB (AlbS), but only either as AlbB homozigotes or AlbAB heterozigotes were observed. There were no AlbA homozigotes. It was not possible to detect relationships between albumin genotypes and early sexual maturity. Regarding transferrin, it was possible to detect two alleles (TfD and TfE). When trying to establish a relationship between transferrin electrophoretic pattern and the desirable economic trait (early sexual maturity) it is suggested that the TfD allele could be associated with bulls that probably will provide freezable semen at an early age.