A fluorescence microscopic method was applied for the histochemical studies of vitamin B_6. The techniques of the method were described. The distribution of vitamin B_6 in various tissues of albino rat was studied histochemically, and revealed that vitamin B_6 is distributed abundantly in liver, kidneys, and heart, followed by in stomach, small intestine, pancreas, spleen and brain. It was interesting that the distribution of vitamin B_6 was recognized remarkably in β-cells of Langerhans islets. From the histochemical pictures of vitamin B_6 in normal and alloxan-diabetic rats, the absorption, storage and excretion in living bodies were discussed.