In the proposed system for genetic nomenclature of the immunoglobulin loci of the mouse, the heavy-, kappa-, and lambda-chain regions are designated Igh, Igk, and Igl, respectively. The constant subregions are designated Igh-C, Igk-C, and Igl-C, and individual loci in these subregions are designated by Arabic numbers following the hyphen and assigned chronologically, for example, Igh-1, Igh-2, Igl-1, etc. The variable subregions are designated Igh-V, Igk-V, and Igl-V, and individual loci in these subregions are designated by a two- or three-letter symbol or two letters and a number following the hyphen, for example, Igh-Dex, Igh-Pc, and Igk-Ef 1. The symbol following the hyphen for variable-region loci should be related to the antigen for which the immunoglobulin is specific or to the method used for recognizing the variants. © 1979 Springer-Verlag New York Inc.