The eukaryotic cell cycle comprises two critical phases, DNA replication (S phase) and the subsequent distribution of an equivalent genome to each of two daughter cells at mitosis (M phase). A signal transduction cascade called the replication checkpoint has evolved to ensure that M phase does not occur prior to the completion of S phase. The mitotic regulators targeted by this checkpoint have recently been identified in the fission yeast Schizosaccharomyces pombe. As was the case for the DNA damage checkpoint, studies on the replication checkpoint in fission yeast promise to provide an excellent framework for analogous studies in mammalian cells.