Two rabbit germline bacterial artificial chromosome (BAC) libraries from animals with the b5 and b4 allotype were screened with probes specific for the immunoglobulin kappa1 light chain locus. Two partially overlapping BAC clones containing Vkappa elements of b5 allotype were isolated from the b5 library and one BAC clone containing Jkappa1, Ckappa and Vkappa was isolated from the b4 library. These three BAC clones were sequenced. They span about 0.4 MB of the rabbit Ig kappa1 light chain locus including 36 Vkappa elements, five J elements and the coding region of Ckappa1. The organization of the locus and the potential function of newly identified functional and structural elements are discussed.