Abstract: A catheter system for implanting an endoprosthesis at a treatment site in a patient's body lumen. The catheter includes an elongated shaft outer member and a stent sheath distal portion and a self-expanding stent radially restrained in a collapsed configuration within the stent sheath distal portion. A balloon catheter dimensioned for relative axial movement within the shaft outer member has an elongated shaft having an inflation lumen and a device receiving lumen. A stent stop secured to the balloon catheter is reversibly radially expandable to deploy from a collapsed to a radially expanded configuration. In the expanded configuration, the stent stop prevents longitudinal displacement of the stent. A balloon is located on a distal shaft section is releasably locked with respect to the shaft outer member and slidably disposed therein in an unlocked configuration.