Several yeast strains of the species Saccharomyces cerevisiae, S. bayanus and S. paradoxus, first identified by hybridization experiments and measurements of DNA/DNA homology, were characterized using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) analysis of the MET2 gene. There was no exception to the agreement between this method and classical genetic analyses for any of the strains examined, so PCR/RFLP of the MET2 gene is a reliable and fast technique for delimiting S. cerevisiae and S. bayanus. Enological strains classified as S. bayanus, S. chevalieri, and S. capensis gave S. cerevisiae restriction patterns, whereas most S. uvarum strains belong to S. bayanus. Enologists should no longer use the name of S. bayanus for S. cerevisiae Gal strains, and should consider S. bayanus as a distinct species.