Abstract: An inline intravenous final filter unit especially of the bacteria-retentive type and adapted to be incorporated in administering sets for administering infusion solutions to patients. The filter unit comprises a casing having an inlet cap at its one end and an outlet cap at the other end thereof, at least one porous hollow fiber arranged within the casing in parallel to the longitudinal direction thereof and having a porosity rating of 0.1 to 5.mu., the hollow fiber being closed at its one end opposed to the inlet cap and open at the other end thereof opposed to the outlet cap, the hollow fiber further being tightly fixed at the outer peripheral portion of its open end to the inner wall of the casing by a securing member, and the ratio of the total effective filtration area of the hollow fiber to the capacity of the casing being at least about 4:1.