The rho genes encode a group of low-molecular-weight GTP-binding proteins that show about 30% identity in the amino-acid sequence to the ras gene product. Two cDNA clones, both of which are similar to the rho genes, were isolated from a cDNA library of the fission yeast Schizosaccharomyces pombe, using the human rhoA cDNA as a probe. These genes were called rho1+ and rho2+. The encoded Rho1 protein showed 72.7% identity to the budding yeast RHO1 and 66.8% to human RhoA, and the encoded Rho2 protein showed 53.2% identity to the budding yeast RHO2 and RhoA.