The clinical application of the separator in the treatment of 4 patients suffering from Waldenstrom's macroglobulinemia,acute myelocytic leukemia, chronic lymphocytic leukemia and polycythemia vera was reported. With exception of one case of acute myelocytic leukemia, in which the WBC count in peripheral blood did not show marked decrease, all other 3 cases showed marked improvement in blood picture after separation. The blood sample cultures of 4 cases for bacteria were negative, suggesting the sterilization efficacy of ethylene oxide vapour to the bowl and polyvinyl chloride tubes in the CFBCS system was reliable.Hep-arinization with a dose of 80 u/kg showed safe anticoagulation effect. The causes of chilliness, rigor and fever,and the factors influencing the fluency of blood flow were discussed. The preventive measures were suggested.