Leukocyte filter

The present invention relates to leukocyte filters and filtration generally. There is provided a leukocyte filter comprising: a prefilter portion; and a membrane filter portion downstream of the prefilter portion, the membrane filter portion having a pore size distribution having a median pore size between 3 and 12 microns and having at least 40% of the pore volume being constituted by pores having a pore cross section diameter of between 3 and 10 microns and having at least 5% of the pore volume being constituted by pores having a pore cross section diameter larger than 10 microns. In a preferred embodiment, no more than 60% of the pore volume is constituted by pores having a pore cross section diameter larger than 10 microns. In another preferred embodiment, the membrane filter portion is characterized in that no more than 30% of the pore volume is constituted by pores having a pore cross section diameter less than 3 microns. In a preferred embodiment, the membrane filter portion is characterized in that no more than 30% of the pore volume is constituted by pores having a pore cross section diameter less than 3 microns. There is also provided a filtering method and a filtered blood product, including a filtered whole blood product.