An insertion system for release of a self-expanding stent device (18) in a body vessel comprises a first grip (33), which is fixedly connected to a shaft (15), a second grip (36), which is mounted on the shaft (15) to be movable in axial direction, a sheath (19), which, in a distal portion thereof, keeps the stent device radially compressed and which is fixedly connected to the second grip (36), and a retention element (17), which is fixedly connected to the shaft (15) and is guided in the sheath (19), wherein the retention element (17) holds the stent device (18) in its axial position relative to the first grip (33) when the sheath (19) is being retracted. Reference means (25) with an optical reference mark (26) are provided for continuous monitoring of the axial position of the stent device (18). ( Fig. 6 )
