Abstract: A method and apparatus for applying a polymer coating on an elongated substrate, preferably an elongate intracorporeal device in the form of a guidewire. An extrudable polymer cartridge is moved by a cartridge advancement mechanism into a guide chamber which is heated at an end with a die or orifice through which a desired portion of a guidewire may pass and be coated. Parameters such as guide chamber temperature, pull speed and force exerted by the cartridge advancement mechanism may be controlled with a computer program in order to achieve repeatable results. The guide chamber, extrudable polymer cartridge, die, and push tube may all be made from polymer components which can be reused or disposed of after a single use.