In an attempt to clarify the effects of various antileukemic agents on cell division and on the multiplication of leukemic cells, the author performed the bone-marrow tissue culture of various leukemic patients in fluid media. Namely, the author observed the effects of direct addition of urethane, nitromin, myleran, tespamin, colcemid, carzinophilin, actinomycin C, chromomycin, and mitomycin on the changes in the leucocyte count by performing bone marrow tissus culture in fluid media of various leukemic patients, and obtained the following results: 1. In acute myelogenous leukemia nitromin acted inhibitorily a little on the increase of leukocyte count. 2. In chronic myelogenous lcnkemia the inhibitory effect was marked in the descending order of myleran, carzinophilin, nitromin and urethane. 3. In acute lymphocytic leukemia all agents hardly had any inhibitory effect on the increase in the leucocyte count, but nitromin was slightly effective. 4. In chronic lymphocytic leukemia the inhibitory effect was marked in the descending order of nitromin, actinomycin C and tespamin. 5. In monocytic leukemia the inhibitory effect was found to be in the descending order of mitomycin and nitromin. 6. From these experiments, clinically it can be anticipated that nitromin is effective in acute myelogenous leukemia; myleran and carzinophilin in chronic myelogenous leukemia; nitromin and actinomycin C in chronic lymphocytic leukemia; and mitomycin in monocytic leukemia.