Abstract: An improved gas venting valve is provided for use with a material-forming mold or die cavity to control venting of gas through a gas conduit communicating with the cavity. The gas venting valve includes a hollow piston axially movable in a housing and having a valve head connected thereto for movement between open and closed positions relative to a valve seat. The valve seat is disposed in a portal of the housing communicating with the gas conduit. In the open position, a gas venting passage internal of the piston is communicated to the portal by the open valve for venting gas from the cavity as material is introduced therein. In the closed position, the valve head is sealed against the valve seat to prevent material introduced into the mold cavity from escaping. The piston is axially moved in the housing by application of pressurized fluid to respective pressure responsive surfaces on the piston.