Various receptor data were collected, edited and integrated into an Integrated Receptor Database (IRDB). The data stored includes structural data (amino acid sequences, their secondary-structure and three-dimensional structure), functional data, binding affinity, cell signaling data etc. The purpose of this database is to allow structural biologists, drug designers and toxicologists to analyse and elucidate receptor-ligand dockings and the resultant post-binding signal transduction pathways. IRDB is available on line (http://impact.nihs.go.jp/RDB.html)