IMGT, the international ImMunoGeneTics information system® (http://imgt.cines.fr), is a high quality integrated information system specializing in immunoglobulins (IG), T cell receptors (TR), major histocompatibility complex (MHC) and related proteins of the immune system of human and other vertebrates, created in 1989, by the Laboratoire d’ImmunoGénétique Moléculaire (LIGM), at the Université Montpellier II, CNRS, Montpellier, France. IMGT is the global reference in immunogenetics and immunoinformatics and provides a common access to standardized data which include nucleotide and protein sequences, oligonucleotide primers, gene maps, genetic polymorphisms, specificities, 2D and 3D structures. IMGT includes three sequence databases (IMGT/LIGM-DB, IMGT/MHC-DB hosted at EBI, IMGT/PRIMER-DB), one genome database (IMGT/GENE-DB), one 3D structure database (IMGT/3Dstructure-DB), Web resources comprising 8000 HTML pages (“IMGT Marie-Paule page”) and interactive tools for sequence (IMGT/V-QUEST, IMGT/JunctionAnalysis, IMGT/Allele-Align, IMGT/PhyloGene) and genome (IMGT/GeneSearch, IMGT/Gene View, IMGT/Locus View) analysis. IMGT data are expertly annotated according to the rules of the IMGT Scientific chart, based on the IMGT-ONTOLOGY concepts. IMGT tools are particularly useful for the analysis of the IG and TR repertoires in physiological normal and pathological situations. IMGT has important applications in medical research (repertoire analysis in autoimmune diseases, AIDS, leukemias, lymphomas, myelomas), biotechnology related to antibody engineering (phage displays, combinatorial libraries) and therapeutic approaches (graft, immunotherapy). IMGT is freely available at http://imgt.cines.fr.