A delivery system (10) for implanting a medical device (30) such as a venous valve into the vasculature of a patient. The delivery system includes a delivery catheter (11) having a device-containing portion (15) adjacent to the distal end (14) thereof, and an inner member (16) extending through the catheter and beyond the distal end thereof, to an atraumatic distal tip portion (17) forward of the catheter distal end. The inner member extends through the medical device in the device-containing region, includes a proximal portion (18) with a sufficiently large diameter to prevent longitudinal movement of the device as the catheter is retracted during deployment, and centers the device upon release from the distal catheter end during deployment.