Apparatus and methods for mixing and dispensing components. The methods and apparatus of the invention are particularly advantageous to mix the components of radiopaque bone cement and inject the resulting radiopaque bone cement into skeletal structures. The apparatus of the invention comprises: (1) a sealed mixing chamber for mixing components; (2) a dispensing chamber isolated from the sealed mixing chamber; (3) a controllable portal to open a flow path between the sealed mixing chamber and the dispensing chamber so that the dispensing chamber can receive the mixed components after they are mixed; and (4) a drive mechanism associated with the dispensing chamber to force the mixed contents from the dispensing chamber.