IMGT, the international ImMunoGeneTics database (http://imgt.cines. 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 ). At present, IMGT includes two databases: IMGT/LIGM-DB, a comprehensive database of Ig and TcR from human and other vertebrates, with translation for fully annotated sequences, and IMGT/HLA-DB, a database of the human MHC referred to as HLA (Human Leucocyte Antigens). The IMGT server provides a common access to expertized genomic, proteomic, structural and polymorphic data of Ig and TcR molecules of all vertebrates. 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.cines.fr:8104. The IMGT Index is provided at the IMGT Marie-Paule page (http://imgt.cines.fr:8104/textes/IMGTindex.html).