Abstract: A syringe for the gravity-feed intravenous administration of drugs and the like comprises three hollow, elongated, cylindrical, outer, middle and inner barrels nested concentrically and tandemly within each other and means for suspending the syringe above a patient. The middle barrel has an open end with a rubber stopper on it slidably and sealingly disposed within the outer barrel to adjustably define a liquid-receiving volume therein. The inner barrel has a hollow interior, an open external end containing a microbial filter through which its interior is vented to ambient pressure, and a closed end having a sharp, hollow needle communicating with the interior and extending outwardly therefrom. Selective advancement of the inner barrel toward the rubber stopper causes the needle to penetrate the stopper and vent the volume to ambient pressure through the interior of the inner barrel and the filter, whereby liquid medication in the volume may gravity-feed through an established primary or secondary I.V.