Six species of the genus Polyporus s. str. from which monosporic cultures were obtained, were studied to investigate their sexual compatibility. All species tested have an heterothallic multifactorial tetrapolar system. Results of intraspecific matings indicated a certain reproductive isolation of the Argentine and Brazilian collections of P. tenuiculus. Interspecific matings confirmed the separation of the species P. ciliatus and P. tucumanensis, as well as P. dictyopus and P. melanopus. Di-mon matings allowed the separation of P. tenuiculus from P. philippinensis.