The invention relates to a preparation and application device for materials which are to be prepared as a paste-like, flowable mass from at least one powder or granulate component and one liquid component, especially bone cement, with an elongated mixing cylinder for receiving the components to be mixed, comprising in one end region a sealable through-opening that can optionally be provided with a discharge unit for the paste-like material to be prepared, and a piston which can be inserted into the other, opposite, open end. The piston is displaceable in the cylinder and seals against the inner wall of the cylinder. The piston is penetrated by an elongated mixing shaft sealed against the piston, and a mixing mechanism is disposed at the cylinder inside-end of the mixing shaft and a handle disposed at the cylinder outside-end of the mixing shaft. The open end of the cylinder located opposite the through-opening and receiving the piston is additionally provided with a removable sealing cap that can be secured on and removed from the cylinder or piston and has a through-opening for the mixing shaft. The piston on the side of the sealing cap has a vacuum fitting adapted for connection to a vacuum source, which can produce a vacuum in the interior of the cylinder through a passageway provided in the piston. The sealing cap includes a through-opening through which the vacuum line that is connected to the vacuum source can be connected to the vacuum fitting in the piston.