In order to observe the influence of Bleomycin on the bone marrow thrombopoiesis, clinical tissue culture of bone marrow from normal guinea pigs was conducted. Bleomycin solutions at various concentration were added directly to the culture media and observations were carried out to see effect of Bleomycin on the function of megakaryocytes of bone marrow. The results obtained show that the thrombopoietic functions of bone marrow were not inhibited in the medium containning 0.0005mg/ml, 0.05mg/ml and 5mg/ml of Blomycin.