The main problem when machining MMC is the extensive tool wear, caused by the very hard and abrasive reinforcements. In order to examine the efficiency of different cutting materials, such as cemented carbide and diamond, milling-, drilling-, reaming-, and threading-tests were carried out as well as tests with different workpiece materials. Squeeze-cast workpiece materials were machined consisting of an AZ91 magnesium alloy with 20 vol.% delta-Al2O3 short fibres and one with 20 vol.% carbon fibres. Besides tool wear, another important factor is the surface integrity of MMC. In the case of the subsurface zone of the workpiece machined with worn. cutting tools the reinforcements are fractured as a result of plastic deformation. Damage of the reinforcements, caused by the machining process, can lead to a deterioration in the properties of the components.