TreeBASE is a relational database of phylogenetic information hosted by the Yale Peabody Museum. In previous years the database has been hosted by University at Buffalo, Harvard University Herbaria, Leiden University EEW, and the University of California, Davis. TreeBASE stores phylogenetic trees and the data matrices used to generate them from published research papers. We encourage biologists to submit phylogenetic data that are either published or in press, especially if these data were not fully presented in the publication due to space limitations. TreeBASE accepts all types of phylogenetic data (e.g., trees of species, trees of populations, trees of genes) representing all biotic taxa. For more information, see an introduction to TreeBASE, information on searching, the database schema, and a graphic presentation of the web site's internal structure. Also, check out some ideas on why you might want to use TreeBASE. TreeBASE is now a participant in CIPRes , the NSF-sponsored Cyberinfrastructure for Phylogenetic Research project. As such, it is being redesigned from the ground up through collaborative research among Computer Scientists, Biologists, and Programmers. Presently TreeBASE is being mirrored at the San Diego Supercomputer Center at UCSD. Eventually, the redesigned, new and improved CIPRes version of TreeBASE will take over. In the meantime, please send us suggestions of what kinds of features or functions would you like designed into the new database? Are there new or unusual data types , queries, and functions that are not already offered by the current version of TreeBASE? Please send your suggestions here (but replace the " at " in the address with "@"). The WWW implementation of TreeBASE requires a forms-capable and frames-capable browser. We would be very grateful for any feedback on TreeBASE, including suggestions for improvement. In particular, if you encounter any errors please let us know.