Abstract: A single-use safety syringe comprising an outer cylindrical body provided with an end spout, a needle provided with a joint adapted to releasably engage the inner wall of the end spout, and a plunger provided with a fore end adapted to releasably inwardly engage the joint of the needle so as to allow the plunger to move into the syringe and engage the end spout to make the injection. The joint has an inner seat with a widening plug projecting downwardly from a base of the seat and projections extending from walls of the seat. The fore end of the plunger has a conical axial cavity open at a frontal face of the fore end and cuts along its generatrix and a groove there around.