Abstract: A blood filter in which the pore size of the filtering media generally decreases through a series of at least three stages where the filtering capacity of at least the first stage is chosen so as to accommodate without substantial impairment of function the quantity of large particle size debris which is normally present in a predetermined amount of blood. The filtering media is composed of several plies of porous material including both depth and screen filter elements. These filter elements are arranged in one or more elongated bands. The bands are spirally wound into a cylindrical form around a generally rigid, perforate core. The ends of the spirally wound cylindrically configured filter are sealed to produce a filter cartridge. The filter cartridge is in turn sealed into a container which has blood inlet and outlet ports arranged so that blood normally flows radially inwardly through the filter.