GENETICALLY controlled variations in the haptoglobins (α2-globulins) of human serum have been demonstrated by electrophoresis in starch gels1–3. The frequencies of the genes controlling these proteins probably differ from one racial group to another4. Inherited differences in the serum proteins of dairy cattle have also been established using the same method, but in cattle the variable proteins prove to be β-globulins5. The frequencies of the genes involved differ in different breeds. This communication reports variations in human serum β-globulins which have now been found.