The budding yeast, Saccharomyces cerevisiae, has long been used as a model system to study the functions of human genes. Now that the genome sequences from several other fungal species are nearly complete, we can characterize the genetic diversity in the fungal kingdom at the genomic level. This diversity means that the number of human genes with homologues in the fungal kingdom is double that with homologues in S. cerevisiae only. Therefore, functional studies of human genes in the fungal model systems should look beyond S. cerevisiae.