The oncogenes of Harvey and Kirsten murine sarcoma viruses (v-rasH and v-rasK) and their cellular homologues (c-rasH and c-rasK) constitute two members of the ras gene family. Each functional member of the ras gene family encodes a 21,000 molecular weight protein (p21ras). ras genes have been detected in a wide variety of vertebrate species, including Xenopus laevis (R. E. Steele, personal communication), and in Drosophila melanogaster. We report here the detection of ras-related genes in the yeast Saccharomyces cerevisiae, and the isolation of two ras-related molecular clones, c-rassc-1 and c-rassc-2, from the DNA of Saccharomyces. Both c-rassc-1 and c-rassc-2 hybridize specifically to probes prepared from mammalian ras DNA. Sequencing of c-rassc-1 reveals extensive amino acid homology between the protein encoded by c-rassc-1 and the p21 encoded by c-rasH. Our studies suggest that these clones can be used to elucidate the normal cellular functions of ras-related genes in this relatively simple eukaryotic organism.