We isolated two sterile mutants of Schizosaccharomyces pombe. One of them was mapped close to ste13 (8 cM). Since it turned out to be allelic with the hitherto unmapped ral2, its linkage with ste13 localizes ral2 on the right arm of chromosome II. The other mutant defines a novel class-I ste gene, ste15, closely linked to ste7 (4 cM) on chromosome I. ste15 is conjugation-specific and acts upstream of pat1 and ras1. During its genetic analysis, a phenotypic suppression of ste12-N9 was observed which was caused by mutations in the unlinked gene ssw1.