This publication presents the SWISS-2DPAGE database which gathers data on proteins identified on various two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) maps. Each SWISS-2DPAGE entry contains data on one protein, including mapping procedures, physiological and pathological data and bibliographical references, as well as several 2-D PAGE images showing the protein location. Links are also provided to other databases such as SWISS-PROT, EMBL, PROSITE and OMIM. The database has been set up on a server which may be accessed from any computer connected to the internet and it also makes it possible to display the theoretical location of proteins, the positions of which are not yet known on the 2-D PAGE.