Abstract: A method and apparatus for mixing bone cement which produces bone cement essentially free of entrained air. The apparatus includes a cartridge having two telescoping cylinders. The outer cylinder receives a cap thereon which hermetically seals the cartridge. The cap includes an outlet port in which a break-away agitator is installed and a port for connection of a vacuum pump. In use, a desired vacuum pressure is drawn on the cartridge and the inner cylinder is allowed to be drawn into the outer cylinder while the vacuum is being drawn, whereupon the inner cylinder automatically stops moving relative to the outer cylinder when the desired vacuum pressure is reached. Mixing of the bone cement is then performed under the partial vacuum thereby created. The agitator paddles provide a scraping action against both inner cylinder walls of the telescoping cylinders thereby improving mixing.