For the purpose of observing the extramedullary hematopoiesis in the tissue of low oxygen tension the author has studied first extramedullary hematopoiesis in the tissues of normal rabbits introducing homologous bone-marrow cells intravenously by Osogoe's method, and reconfirmed Osogoe's initial findings; and obtained the following results: 1. Twenty-four hours after the injection the bone-marrow cells were found accumulated mainly in the capillary of the lungs and a small number in the liver, spleen and kidneys. 2. After three days their number decreased considerably in the lungs with a moderate increase in the liver and kidneys, and after seven days they have actually disappeared in every organ. These findings indicate that in normal rabbits the extramedullary hematopoiesis caused by the injection of bone-marrow cells is only a transient one.