Abstract: A variable length balloon catheter having an inner tubular member extending over the length thereof with a guide wire lumen therethrough. The distal waist of a balloon is affixed proximate the distal end of the inner tubular member while the proximal end or proximal waist of the balloon extends into and is slidably received within an outer tubular member. Means for sealing or preventing fluid flow between the proximal waist and inside diameter of the outer tubular member are provided. The means for sealing can include a passive or close tolerance seal assembly, an active seal assembly, or an axially elongatable membrane seal assembly. Axial movement of the inner tubular member varies the length of balloon extending distally beyond the distal end of the outer tubular member, thus determining inflated balloon length.