Methods for making medical devices and portions of medical devices (e.g., intravascular catheters, catheter shafts, and tubular guiding members) are provided. Example methods may include providing a first ribbon comprising one or more thermoplastic materials and a piece of shrink tubing defining a shrink tube lumen and forming a first assembly by positioning the first ribbon inside the shrink tube lumen and urging the first ribbon to assume a tubular shape in which the first ribbon defines a ribbon lumen. A second assembly may be formed by loading an inner tubular member over a mandrel and forming or placing a support structure over an outer surface of the inner tubular member. A third assembly may be formed by inserting the second assembly into the ribbon lumen defined by the first ribbon of the first assembly. The third assembly may be heated to a process temperature.
