The Schizosaccharomyces pombe pac2 gene encodes a protein of 235 amino acids not similar to any protein of known function. Cells over-expressing pac2 were poor in mating and sporulation. Expression of ste11, which encodes a key transcription factor for sexual development, was not inducible by nitrogen starvation in these cells. Cells defective in pac2 could express ste11 and enter sexual development under incomplete starvation conditions. Although expression of ste11 is regulated primarily by the cAMP cascade, genetic analysis indicated that this cascade and pac2 can partially compensate for each other in the regulation of sexual development, and that neither of them is epistatic over the other. Thus, Pac2 appears to control ste11 expression via a signaling pathway independent of the cAMP cascade.