We have cloned and determined the complete nucleotide sequence of a RAS gene from the yeast Schizosaccharomyces pombe (SP-RAS). The putative RAS protein of 214 amino acids is encoded by two noncontiguous reading frames separated by an intron of 86 bp. The SP-RAS gene product shares extensive homology with the proteins of the Saccharomyces cerevisiae (SC), Dictyostelium, Drosophila, and human RAS genes in its N-terminal region but not in its C-terminal region. The extended C-terminal regions found in the SC-RAS genes have no counterpart in the SP-RAS gene. Thus the RAS genes of these two yeasts are structurally quite distinct. The SP-RAS sequence was expressed in vivo.