A perfusion dilatation catheter is disclosed which has an improved distal catheter shaft portion with a tubular member extending within the balloon provided with an expanded coil support incorporated within the wall of the tubular member. The coil is preferably closer to the inner surface than the outer surface of the tubular member. Also disclosed are improved catheter shaft sections in a perfusion portion proximal to the balloon, one with a reinforced inflation tube depending into the guidewire lumen and another having three separate lumens, a central guidewire lumen and a pair of inflation lumens on opposing sides of the tubular structure defining the guidewire lumen.