Abstract: Disclosed is a cylindrical balloon mounted near the distal tip of a percutaneous transluminal laser angioplasty catheter. Proximal and distal neck sections of the balloon are sealed to the catheter tubing, and a balloon inflation lumen originating at the tubing proximal end is open to the balloon interior. An elongate cylindrical body of the balloon is joined to the distal neck by a substantially transverse distal wall. As the balloon dilates in response to fluid under pressure supplied to the lumen, the distal wall tends to position the distal neck and distal end of the catheter tubing in centered, coaxial relation to the balloon body.