Abstract 1. 1. Serum transferrins were analyzed by strach-gel electrophoresis from thirteen Canadian and Alaskan populations of Spermophilus undulatus (Pallas). Five molecular forms of transferrin, Tf 5–9, are found in this species and all but Tf 5 were observed in the study. 2. 2. Examination of an interbreeding population displaying three Tf alleles indicates that the single or double fractions found in individual animals reflect homozygosity or heterozygosity respectively. 3. 3. Transferrins suggest that S. undulatus osgoodi (Tf 6) of central Alaska evolved from arctic population of S. undulatus parryii (Tf 6, 7, 8) rather than S. undulatus ablusus (Tf7) or S. undulatus plesius (Tf 5,7) frmo subarctic Alaska and Canada. 4. 4. The use of transferrins in establishing the geographic distribution of S. undulatus plesius and s. undulatus ablusus and in evaluating evolution within certain populations of S. undulatus parryii is discussed.