The tribe Maximae (Panicum maximum Jacp., P. infestum Anders., P. trichocladum K.Schum.) includes two sympatric pools with different modes of reproduction and ploidy levels: an apomictic and tetraploid pool on the one hand, and a smaller, sexual and diploid pool on the other. In the latter, the sexuality allowed crosses and hence it was possible to gather evidence of the structure (monomeric or dimeric) of nine enzymatic systems and of their inheritance (16 loci). Some segregation distortion was observed in the malatedehydrogenase and esterase systems. The genetic diversity of the diploid pool is large, in agreement with its mode of reproduction (allogamy and anemophily). The diversity is divided into three groups corresponding to the geographical origin of populations. This organisation is very similar to that observed from morphological traits.