1. Vitamin B12 serum concentrations have been investigated in various types Of leukemia.
2. The concentration in chronic myeloid leukemia is approximately 15 times normal. In chronic lymphatic leukemia it is normal. In acute leukemia it is variable.
3. In chronic myeloid leukemia, the serum vitamim B12 exists in the bound form and the binding capacity for added B12 is increased.
4. Electrophoretic studies indicate that serum vitamims B12 in chronic myeloid leukemia is bound in the alpha globulin fractions.
5. Some correlation was found between serum vitamin B12 concentrations and total white cell counts in chronic myeloid leukemia. The possible significance of this is discussed.