Background: Tem1 is a low-molecular-weight GTP-binding protein (GTPase) which is required for the termination of M phase in cell division. The defect of Tem1 was lethal, and the Tem1-defective cells were arrested at telophase with high H1-kinase activity, indicating that Tem1 is required to exit from M phase. The defect of Tem1 was suppressed by a high dose of cdc15, which encodes a protein kinase. Tem1 functions upstream of cdc15 kinase and may be required to activate the cdc15 protein kinase pathway. A cascade consisting of Tem1 and kinases act to terminate mitosis.