In the present report are presented the results of the clinical and statistical observations conducted on the hemomyelogram of various leukemias occurring in the Chugoku-Shikoku District, with a special reference to the comparative studies carried on the bone marrow of patients treated in our department, handling the cases in which bone-marrow tissue culture was conducted and those without the tissue culture separately. It is to be noted that chronic lymphocytic leukemia is not included in the present study as the number of such cases was to small. 1. In every leukemia generally immature cells are markedly increased in number; in acute leukemia blast cells occupy the major proportion; and in chronic leukemia young leucocytes in various stages of maturation are mixed. 2. Judging from the hemomyelogram, all cases of monocytic leukemia seems to occupy an intermediate position between acute leukemia and chronic leukemia. Hence it is difficult to divide it definitely as an acute leukemia or a chronic one. 3. It is worthy of attention that monocytic leukemia in the cases given no bone-marrow tissue culture occupies only 9.8 per cent of the total leukemia, whereas the same in the cases given the bone-marrow tissue culture occupies as much as 45.5 per cent of the total leukemia. Namely, it is to be noted that without the bone-marrow tissue culture it is often difficult to diagnose monocytic leukemia correctly and it is often mistaken for other leukemias, especially for acute myelogenous leukemia.