The 'Mouse (Mus musculus) Immunoglobulin Kappa Variable (IGKV) Genes and Joining (IGKJ) Segments', third report of the 'IMGT Locus on Focus' section, comprises four tables entitled: (1) 'Mouse (Mus musculus) germline IGKV gene table'; (2) 'Correspondence between Mouse (Mus musculus) IMGT IGKV subgroups and previous designations'; (3) 'Mouse (Mus musculus) germline IGKJ table', and (4) 'Mouse (Mus musculus) IGKJ allele table'. These tables are available at the IMGT Marie-Paule page from IMGT, the international ImMunoGeneTics database (http://imgt.cnusc.fr:8104) created by Marie-Paule Lefranc, CNRS, Université Montpellier II, Montpellier, France.