Abstract: The present invention relates to a mixing device for producing bone cement by mixing components intended therefor, wherein the bone cement (3) is made by mixing the components (4, 5) under a vacuum in a mixing space (6), and wherein the mixing space (6) includes at least one piston (9) which can be brought to remain in a start position (A) during mixing and which is releasable therefrom after mixing, whereby said piston (9) will be sucked into the mixing space (6) by being affected by the vacuum prevailing therein. At least one throttle device (20) is provided for generating a pressure drop between the air pressure in the surroundings and the piston (9) for preventing full power affection thereof by said air pressure. At a method in connection with said device, the piston (9) is brought to remain in the start position (A) during mixing of the components (4, 5) by air-tight isolation thereof from the surroundings. The piston (9) can be released from the start position (A) by opening the air-tight isolation.