For the purpose of observing the influences of chloroquine on the bone marrow erythropoiesis, a roller tube culture method was used to cultivate bone marrow cell suspension from normal rabbits. Chloroquine diphosphate at various concentrations were added directly to the culture media and observations were carried out on the increase rate of erythrocytes, increase rate of nucleated cells, increase of hemoglobin content and percentage of orthochromic erythroblasts. As a result, it has been shown that the erythropoietic functions of bone marrow were hardly inhibited in the medium containning 2γ/dl of Chloroguine, and were slightly inhibited in the medium containning 20γ/dl of chloroquine, but were markedly inhibited in the medium containning 200γ/dl and 2000γ/dl of chloroquine.