This paper describes a procedure for determining defroster performance using wax. The approach is a useful tool for establishing breakthrough points, and developing balanced defroster air distribution patterns prior to cold room testing. Since it can be conducted at room temperature, the wax method is considerably more convenient and can be executed with greater frequency than in a cold room.Although the wax procedure is a good barometer of the relative effectiveness of different defroster systems, and does provide valuable preliminary studies, it does not duplicate cold room conditions. The test method described, therefore, is not a substitute for, nor can it be used in place of, actual cold room testing. The paper provides information on the test facility, test equipment, test preparation, wax mixture and application, and conducting the test.