In this research, poly(butylene terephthalate) (PBT) electrospun nanofibrous mats were prepared for white blood cell (WBC) filtration after the blood was collected from donors. The feasibility of using PBT electrospun mats used as WBC filtration materials was studied. The average fiber diameter and mean pore diameter of the PBT electrospun mats were much lower than those of melt-blown mats, and such properties were found to be beneficial for the functions of filtration and cell absorbency. A layer of PBT electrospun mats was added before the exit of filter; this formed a kind of compound material with different pore diameters and fibers diameters in the direction of blood flow. The WBC filtration efficiency of the newly designed filter and a traditional filter were also compared. The results show that filters with electrospun PBT fibers reduced the number of WBCs to 104/L, whereas the remaining WBCs after flow through the traditional filter was about 105L1. The existence of electrospun fibers increased the filtration resistance at the same time, and this led to a longer filtration time. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013