JenPep is a relational database containing a compendium of thermodynamic binding data for the interactionof peptides with a range of important immunological molecules: the major histocompatibility complex,TAP transporter, and T cell receptor. The database also includes annotated lists of B cell and T cell epitopes.Version 2.0 of the database is implemented in a bespoke postgreSQL database system and is fully searchableonline via a perl/HTML interface (URL: http://www.jenner.ac.uk/JenPep).