We studied the efficiency in removing leukocytes of a new filter, Sepacell PLX-5A, that is developed to remove leukocytes from platelet concentrates(PC)at the bed-side. Residual leukocytes of filtered PCs were consistently less than 10^5 cells, while the platelet recovery rates ranged from 84 to 89%. The filtration with the filter did not affect platelet functions. According to the AABB technical manual, the leukocyte contents in blood products are recommended to be less than 5×10^6/bag to prevent alloimmunization. The use of Sepacell PLX-5A may help to prevent the alloimmunization on platelet transfusion.