Abstract: Study of hemopoietic activity is a very important topic in Hematology.The growth cytokine-tic activity of bone marrow cells represents hemopoietic status.In the bone marrow smear,onlythe M phase can be identified,whereas the G₁ phase,S phase and G₂ phase are invisible.Byusing the combination method of rat-human hybridization （RHH）,premature chromosome condens-ation （PCC） and sister chromatid differentiation （SCD） techniques,we could see clearly the dif-ferent phases of the cell cycle in cellular growth.By means of this combination technique,westudied the cytokinetics of human bone marrow cells.M₃ cells were used as the PCC-inducer.PEG was used as the fusion agent.BrdU was usedfor the detection and investigation of SCD.4401 hybrid cells were analyzed.The cytokinetic spe-ed of cell growth cycle was estimated by observing the percentages of 1S^-,1S⁺,2S and 2S⁺ ac-cording to the SCD patterns in the interphase and metaphase chromosomes in the rat-haman hybr-id cells.