Abstract: A fastening system for fixing a first assembly unit to a second component for use especially in the motor vehicle industry is presented, which has at least one fastening screw, a corresponding first preassembly thread on the first assembly unit, in which the fastening screw is fixed after the preassembly, and a fastening thread on the first assembly unit or on the second component for fixing the first assembly unit to the second component by means of the fastening screw. The fastening screw has at least two threaded areas for preassembly and for fastening with different thread pitches, wherein the preassembly thread and the fastening thread as well as the threaded areas are provided with different pitches and the second threaded area, which is used for fastening and is facing away from the screw head, has a smaller diameter than the threaded area that is used for the preassembly and is adjacent to the screw head.