IMGT, the international ImMunoGeneTics database (http://imgt.cnusc. fr:8104), is a high-quality integrated database specialising in Immunoglobulins (Ig), T cell Receptors (TcR) and Major Histocompatibility Complex (MHC) molecules of all vertebrate species, created in 1989 by Marie-Paule Lefranc, Université Montpellier II, CNRS, Montpellier, France (lefranc@ligm.igh.cnrs.fr). IMGT comprises three databases: LIGM-DB, a comprehensive database of Ig and TcR, MHC/HLA-DB, and PRIMER-DB (the last two in development); a tool, IMGT/DNAPLOT, developed for sequence analysis and alignments; and expertised data based on the IMGT scientific chart, the IMGT repertoire. By its high quality and its easy data distribution, IMGT has important implications in medical research (repertoire in autoimmune diseases, AIDS, leukemias, lymphomas), therapeutic approaches (antibody engineering), genome diversity and genome evolution studies. IMGT is freely available at http://imgt.cnusc. fr:8104