Abstract: The invention relates to an injection syringe for mixing and applying injection substances having a syringe cylinder and a plunger displaceable therein. The plunger has a stopper at its distal end tightly engaged against the inner surface of the cylinder to form an injection volume in the syringe cylinder. A mixing plunger is displaceable in longitudinal direction and guided through the plunger. The mixing plunger projects from the stopper at its proximal end and, at its distal end, has a mixing piston with at least one opening, passing through the surface of the piston. Injection substances can pass through the one opening when the mixing piston is displaced in the injection volume. An effective thorough mixing of the injection substances takes place through to-and-fro movement of the mixing piston in the injection volume.