Abstract: A sheath arrangement for spiral balloon catheters which permits improved perfusion during dilation of a body vessel. Methods of making the sheath and assembling the sheath onto a balloon and the resulting sheathed balloon catheter are included. A tube sized to fit over a spiral balloon is cut, preferably by laser cutting, to form ribs extending from the tube ends with collars at the distal ends of the ribs. Preferably, the tube ends are trimmed to match the balloon spiral lobes. The sheath is placed over the spiral balloon, bonded to the balloon lobes. The collars are secured to the catheter adjacent to the balloon. When the balloon is expanded to dilate a body vessel, blood can freely pass through the interlobe channels while the sheath prevents entry of arterial intima from entering into the channels. The rib and collar arrangement securely maintains the sheath in place on the balloon.