Abstract: A small diameter dilatation catheter for coronary angioplasty is achieved by providing first and second elongated flexible, thin-wall tubes, each having one or more reinforcing wires encapsulated in the walls thereof and dimensioned such that the second tube may be coaxially disposed within the lumen of the first tube. The preferred material from which the two tubes are fabricated is polyimide. The longitudinally extending reinforcing wires provide the requisite "pushability" characteristics required by PTCA dilatation catheters. The balloon or inflation member has its proximal end bonded to the outer surface of the outer tube and its distal end bonded to the outer surface of the inner tube. Inflation fluid then may be perfused between the I.D. of the outer tube and the O.D. of the inner tube.