The extent of nuclear DNA complementarity was determined for members of the genus Zygosaccharomyces. From these comparisons, nine species have been identified: Z. baillii, Z. bisporus, Z. cidri, Z. fermentati, Z. florentinus, Z. mellis, Z. microellipsoides, Z. mrakii and Z. rouxii. Candida mogii, the proposed anamorph of Z. rouxii, showed low relatedness to all nine species. The recently described Saccharomyces astigiensis and S. albasitensis were conspecific with Z. fermentati, and S. placentae showed high relatedness with Z. rouxii. Growth tests were defined that allow recognition of all Zygosaccharomyces species.