Abstract: A method and apparatus for forming perfusion balloons from thermoplastic materials. A helical member having a cross section corresponding to a desired perfusion channel cross section is placed in a tubular mold in contact with the mold wall. A thermoplastic tube is inserted into the helical member in the mold. The assembly is heated to the glass transition temperature of the tube and the tube is pressurized to expand into contact with the helical member and mold wall. After cooling, the formed balloon is removed from the mold. The helical member has a "T" shaped, or rectangular, or square, or triangular cross section. Limited pre-pressure and pre-stretch are preferably applied prior to the tube expansion and post forming tube conditioning may be used. Axial stretching of the tube in a mold, with our without the helical member, by microprocessor controlled air actuators provides highest quality balloons having selected wall thicknesses.