PIR-International is an association of macromolecular sequence data collection centers dedicated to fostering international cooperation as an essential element in the development of scientific databases. PIR-International is most noted for the Protein Sequence Database. This database originated in the early 1960's with the pioneering work of the late Margaret Dayhoff as a research tool for the study of protein evolution and intersequence relationships; it is maintained as a scientific resource, organized by biological concepts, using sequence homology as a guiding principle. PIR-International also maintains a number of other genomic, protein sequence, and sequence-related databases. The databases of PIR-International are made widely available. This paper briefly describes the architecture of the Protein Sequence Database, a number of other PIR-International databases, and mechanisms for providing access to and for distribution of these databases.