From its origin, the PIR has aspired to support research in computational biology and genomics through the compilation of a comprehensive, quality controlled and well-organized protein sequence information resource. The resource originated with the pioneering work of the late Margaret O. Dayhoff in the early 1960s. Since 1988, the Protein Sequence Database has been maintained collaboratively by PIR-International, an association of macromolecular sequence data collection centers dedicated to fostering international cooperation as an essential element in the development of scientific databases. The work of the resource is widely distributed and is available on the World Wide Web, via FTP, E-mail server, CD-ROM and magnetic media. It is widely redistributed and incorporated into many other protein sequence data compilations including SWISS-PROT and theEntrezsystem of the NCBI.