Numerous Escherichia coli proteins have already been characterized by two-dimensional gel electrophoresis (2-D PAGE), using carrier ampholytes in the first dimension (VanBogelen, R. A., Sankar, P., Clark, R. L., Bogan, J. A. and Neidhardt, F. C., Electrophoresis 1992, 13, 1014-1054). We present here a reference protein map of E. coli obtained with immobilized pH gradients (IPG) and available in a SWISS-2DPAGE format. Out of the protein spots identified in the E. coli gene protein database by Neidhardt's group, 153 have been identified in the E. coli gene protein database by Neihardt's group, 153 have been identified on the E. coli SWISS-2DPAGE database map by gel comparison and most of them were confirmed either by the analysis of amino acid composition (AAC) and/or N-terminal microsequencing. Additionally, five as yet unsequenced proteins were found. The E. coli SWISS-2DPAGE database is part of the ExPASy molecular biology server accessible through the Word Wide Web network.