Abstract: An imaging balloon dilatation catheter having an elongate flexible tubular member with proximal and distal extremities. An inflatable balloon is carried by the tubular member near the distal extremity thereof. The tubular member has a plurality of lumens formed therein, an illuminating set of optical fibers is disposed in one of the lumens and extends through the length of the tubular member. An imaging bundle of optical fibers extends through another one of the lumens of the tubular member. A lens is carried by the distal extremity of the tubular member and supplies an image to the bundle of imaging optical fibers. The flexible elongate member is provided with a flow passage in communication with the interior of the balloon for inflating and deflating the balloon.