The DBF4 gene of Saccharomyces cerevisiae, required for events preceding DNA replication, was isolated and located to 2.8 kb of DNA from chromosome IV. Genetic mapping showed the gene to be linked to TRP1. The DBF4 transcript is 2.4 kb in length and shows periodic regulation within the cell cycle. The peak of expression occurs late in G1, coincident with several genes involved in DNA synthesis. The behavior of the message is consistent with that expected for a stable, cell cycle regulated transcript.