There is disclosed a bone cement mixer 10 comprising first and second coaxially arranged mixing paddles 18, 20； and a drive mechanism e.g. handle and gears coupled to the first and second mixing paddles 18, 20 and having a rotatable input 38. The drive mechanism is configured such that rotation of the rotatable input 38 causes contra-rotation of the first and second mixing paddles 18, 20 with respect to one another i.e. the paddles rotate in different directions. In a second configuration the rotatable input causes the first and second mixing paddles 18,20 to rotate in the same direction.
