The human pathogen Candida albicans grows either as a yeast or in filamentous form. We have determined the sequence of a 1.365 kb genomic C. albicans fragment that complements Saccharomyces cerevisiae ura3 and Escherichia coli pyrF mutations. An open reading frame within this fragment corresponds to a protein of 270 amino acids that shows homology to orotidine-5'-phosphate decarboxylases (ODCases) of other fungal species. The C. albicans ODCase is most closely related to the ODCases of the budding yeasts Kluyveromyces lactis and S. cerevisiae (74% and 71% homology, respectively). Most 5' ends of URA3 transcripts in the authentic host and in the heterologous host S. cerevisiae were found to be identical. These results demonstrate a close taxonomic relationship between non-pathogenic budding yeasts and C. albicans.