Five contigs of the 5' part of the immunoglobulin kappa locus (F. Röschenthaler et al., Eur. J. Immunol. 1999. 29: 2065 - 2071) have been linked by cosmid clones prepared from bacterial artificial chromosomes (BACs) and by PCR. One of the previously defined contigs which contains three pseudogenes (Z7) was shown by fluorescence in situ hybridization to be located near the kappa locus on chromosome 6, but not within the locus; the three Vkappa genes are therefore now classified as orphons. A Vkappa9 / 10 gene, which was sequenced previously, was now localized within the locus, and two additional Vkappa genes were identified, a potentially functional Vkappa24 gene and a pseudogene of the Vkappa9 / 10 family. This brings the number of localized and sequenced Vkappa genes in the locus to 140; 75 of them are functional, 21 potentially functional and 44 pseudogenes. The 5' part of the kappa locus is now one contig of 1.88 megabase (Mb); it comprises 82 Vkappa genes. Other contigs of the locus are 65 kb, 105 kb and 1.04 Mb in size and contain 2, 5 and 51 Vkappa genes, respectively. The contigs are separated by three gaps of 10 - 40 kb each. Detailed restriction maps and other structural details of the kappa locus are deposted in the Internet at http://www.med. uni-muenchen.de / biochemie / zachau / kappa.htm.