A prosthesis delivery device (100) comprises a cannula (160) having an expandable positioning device (120) disposed at the proximal end thereof. A prosthesis (400) is retained on the cannula distal of the expandable device. Expansion of the expandable device by flowing a fluid through the cannula or by moving together the ends (1250, 1260) of an expandable region (1270) retains and centers the delivery device and the prosthesis carried thereon in the vessel and allows repositioning of the prosthesis without contacting the proximal end of the prosthesis with the vessel walls prior to deployment.
