The Schizosaccharomyces pombe sep1 gene encodes a putative transcription factor that is required for cell separation. Among the genes required for septum formation and cytokinesis in fission yeast examined to date, the only one whose mRNA fluctuates significantly during the cell cycle is cdc15. In this study we have examined cdc15 mRNA levels in sep1 mutant and null backgrounds and have found that sep1p function is required for periodic accumulation of cdc15 mRNA. We have also localised sep1p and find that it is a nuclear protein, consistent with its proposed role as a transcription factor.