IMGT, the international ImMunoGeneTics database (http://imgt.cines.fr) is a high quality integrated information system specializing in immunoglobulins (IG), T cell receptors (TR) and major histocompatibility complex (MHC) of human and other vertebrates. IMGT provides a common access to expertly annotated data on the genome, proteome, genetics and structure of the IG and TR, based on the IMGT Scientific chart and IMGT-ONTOLOGY. The IMGT unique numbering defined for the IG and TR variable regions and domains of all jawed vertebrates has allowed a redefinition of the limits of the framework (FR-IMGT) and complementarity determining regions (CDR-IMGT), leading, for the first time, to a standardized description of mutations, allelic polymorphisms, 2D representations (Colliers de Perles) and 3D structures, whatever the antigen receptor, the chain type, or the species. The IMGT numbering has been extended to the V-like domain and is, therefore, highly valuable for comparative analysis and evolution studies of proteins belonging to the IG superfamily.