A filter for intravenous liquid administration is provided having a filter housing (1); a filter chamber (13) in the housing; an inlet member (17) and an outlet member (22) in the housing (1) in fluid flow communication with the filter chamber (13); a filter (11) in the filter chamber (13) from the inlet member (17) to the outlet member (22) so that all through flow must pass through the filter; and dividing the chamber (13) into two portions (15,16), one upstream (15) and one downstream (16) of the filter; a vent (26) in the housing (1) in flow communication with the upstream portion (15) of the filter chamber (13); and a liquid-impermeable gas-permeable porous member (11) disposed across the line of flow through the vent (26), so that all vent flow must pass through the member (11), the member (11) restricting such flow to gas to which it is permeable; the inlet member (17) being shaped for attachment to a supply of liquid (21) for intravenous administration; and the outlet member (22) being shaped for attachment to an intravenous liquid administration apparatus (25).