In independent investigations, reported almost simultaneously (Cohen, 1960; Shreffler, 1960), the authors have described a protein variant system in the serum of mice, involving an electrophoretic difference in the iron-binding beta-globulin component, transferrin, and have shown the difference to be genetically determined by a pair of co-dominant alleles at a single locus. Both reports introduced the same gene symbol, Trf, for this locus, but in one, letter designations were used (Cohen, 1960), making the allele symbols TrfA and TrfB, and the three phenotypes TrfA, TrfAB and TrfB, while in the other, number designations were used (Shreffler, 1960), with the corresponding symbols Trf1, Trf2, Trf-1, Trf-1·2 and Trf-2. To avoid confusion in future reference to this locus, due to the two differing systems of nomenclature, the authors have agreed upon the revised nomenclature proposed in this communication.