POLYMORPHISM in the β-globulins of cattle, giving five phenotypes1,2, and in humans giving three phenotypes (Smithies, O., personal communication), has been described. The present communication concerns polymorphism in the β-globulins of the serum of sheep, giving to date eight phenotypes. The phenotypes are indicated diagrammatically in Fig. 1. The conditions for obtaining these serum protein differences by starch gel electrophoresis are similar to those described for cattle sera1 except that 5–6 hr. is required to achieve adequate resolution of the β-globulins; in this time the trailing edge of the albumin zone migrates 6–7 cm.