Forty-two dikaryotic and 42 monokaryotic isolates, and 34 pairings were examined by horizontal polyacrylamide gel electrophoresis (PAGE) for six enzymatic activities, viz. EST, 6PGD, IDH, MDH, SHDH and SOD. 44 bands were analysed. Numerical analysis of the isoenzymatic patterns was undertaken and compared with those from morphological characters. The analysis of six enzymatic systems showed the existence of four monomorphic systems (IDH, MDH, SHDH and SOD). The sterease system (EST) appears to be polymorphic in Polyporus ciliatus and in populations of P. tenuiculus from Argentina, being monomorphic in the remaining species studied. The 6PGD system is polymorphic in P. tucumanensis and monomorphic in the other species. Predominance of monomorphic enzymes and a clear distribution of the electromorphs among the species, indicates that isoenzymatic analysis is a good taxonomic tool within Polyporus. The low intraspecific variability allowed the use of interspecific differences to separate species. Numerical analysis showed a good correlation between morphological and molecular characters. In the isoenzymatic phenogram the similarity index is high only among very close species, showing a stressed separation of species.