Abstract: A valve especially designed for use in a prosthetic device such as an artificial limb wherein the limb stump is mounted within a mating socket provided by the prosthetic device and is firmly secured therein by vacuum sealing, the valve being is connected to vent the lower portion of the prosthesis socket when manually actuated. The valve includes a central core section of elastomeric material which is formed with a passageway therethrough for venting the prosthesis cavity and which is formed with an enlarged valve chamber and a valve set facing away from the prosthesis cavity. A valve member is mounted in the chamber and is moveable to and from the set to provide sealed and vented positions respectively. The movement of the valve is controlled by a finger engaging button which is in turn biased by elastomeric nodules to move the valve member to its seat thereby sealing the prosthesis chamber.