Histochemical methods designed to demonstrate Zn++, Cu++, Co++, Mg++, Mn++, Fe++ and Fe+++ have been applied to blood smears. Metallic elements have been found only in the leukocytes belonging to the myeloid series of cells. The neutrophil was found to contain Zn++ and small amounts of Cu++; the eosinophil, on the other hand, was found to contain large amounts of Cu++ and smaller amounts of Zn++. Basophils were not reported as they could not be identified. Mg++ and Mn++ were present in both the neutrophil and the cosinophil while Co++ was found only in the cosinophil. Iron in either the ferric or ferrous state was not demonstrated in any of the leukocytes in this investigation.