YPD is a database for the proteins of the budding yeast, Saccharomyces cerevisiae. YPD has two formats: (i) a spreadsheet which tabulates many of the physical and functional properties of yeast proteins, and (ii) the YPD Protein Reports which are formatted pages containing the protein properties, annotations gathered from the literature, and references with titles. YPD is available through the World-Wide Web, through an Email server, and by anonymous FTP. New releases of the YPD spreadsheet are produced every two to four months, and the on-line information is updated daily.