IMGT, the international ImMunoGeneTics information system^® (http://imgt.cines.fr) created in 1989, by the Laboratoire d'ImmunoGénétique Moléculaire (LIGM), Université Montpellier II and CNRS, Montpellier, France, is a high quality integrated information system, secialized in immunoglobulins (IG), T cell receptors (TR), major histocompatibility complex of human and other vertebrates and related proteins of the immune system that belong to the IgSF and Mhc superfamilies. IMGT/LIGM-DB, the first and the largest IMGT database, manages more than 92,000 IG and TR nucleotide sequences from human and 150 other vertebrate species in May 2005. IMGT/LIGM-DB provides expertly annotated sequences and standardized knowledge based on IMGT-ONTOLOGY, the first ontology for immunogenetics and immunoinformatics. The strategy developed by IMGT, for the IG and TR nucleotide sequence annotation, involves two different approaches that depend on the nature of the sequences, genomic DNA (gDNA) or complementary DNA (cDNA).