The budding yeast Cdc6 protein is important for regulating DNA replication initiation. Cdc6p acts at replication origins, and cdc6-1 mutants arrest with unreplicated DNA and show elevated minichromosome loss rates. Overexpression of the related Cdc18 protein in fission yeast results in DNA rereplication; however, Cdc6p overexpression does not cause this result. A recent paper further defines the role of Cdc6p in DNA replication. Cdc6p only promotes DNA replication between the end of mitosis and late G1, and although the Cdc6 protein is highly unstable, neither degradation nor nuclear localization is critical for limiting DNA replication to this interval.