Abstract: Apparatus is disclosed for compression molding a part from a charge having a curable resin therein. Provision is made for defining a vacuum chamber surrounding the mold cavity when the upper and lower dies are brought to a partially closed position. The vacuum chamber includes a vertically movable ring surrounding the upper die which is urged into sealing engagement with a surface surrounding the lower die. The space between the ring and the upper die is sealed with a flexible diaphragm having an inner edge rigidly attached to the upper die and an outer periphery rigidly attached to the ring member thereby permitting relative vertical movement between the ring and die. The mold cavity is rapidly evacuated and then the upper die is brought into a fully closed position while the resin cures.