Abstract: Apparatus and methods are provided for determining the location of a prosthesis previously deployed in a body lumen, and for effecting treatment associated with the prosthesis, including a catheter having a distal end region and at least one prosthesis locator sensor disposed on the distal end region. A therapeutic device may be provided either on the distal end region of the catheter or on a separate catheter which may be positioned over the distal end region. In one embodiment the therapeutic device is a balloon catheter, while the prosthesis locator sensor is a plurality of compliant and resilient fingers projecting perpendicularly from the circumference of the catheter. The plurality of fingers detect the presence of an edge of a prosthesis by direct electrical connection, or inductance or capacitance changes. Methods of localizing prostheses with the apparatus are also provided.