In order to clarify the effects of anti-leukemic clemical agents-antimetabolites (Azan, 6MP, T-431L), hormones (ACTH, Cortisone, Prednisolone)-on the hematopoietic function of bone marrow, especially on the leucocyte series, the author observed the effects of direct addition of these chemical agents on the tissue growth area, the cell density, and the wandering velocity of pseudoeosinophils of the bone marrow by performing the tissue culture of the normal rabbit bone marrow. Likewise, the bone-narrow tissue culture of normal persons has been performed with the addition of several anti-leukemic chemical agents at various concentrations, and established the maximal concentration of the agents in the medium as to not impede the bone-marrow growth; and obtained the following results. 1. Any one of anti-leukemic agents acts inhibitorily on the cell growth and the wandering velocity of the cells of the bone marrow at a higher concentration than at a certain fixed concentration. Of the anitmetabolites used in the present experiments, the inhibitory effect is strong in the descending order of T-431L, Azan and 6MP; and of the hormones it is in the order of Prednisolone, Cortisone and ACTH. 2. The maximal concentration of the media with addition of several anti-leukemic agents, which do not impede the growth of the bone marrow of normal persons is 0.035 mg/ml for Azan; 0.05 mg./ml. for 6MP; 0.01 mg/ml. for T-431L; 0.01 mg/ml. for ACTH; 0.01 mg/ml. for Cortisone ; and 0.01 mg/ml. for Prednisolone.