Magnesium based Metal Matrix Composites (MMCs) reinforced by a combination of short Al₂O₃-fibres and SiC-particles are promising construction materials due to the low density and thermal expansion, high creep and wear resistance. Such a material is the hybrid reinforced magnesium alloy AE42, which is produced by the melt infiltration of fibre-particle preforms in the squeeze casting process. Many problems arise by machining these preforms with common machining tools because of the high wear resistance caused by the ceramic reinforcement. Solutions are only expensive tools with cutting edges made of polycrystalline diamonds or CVD-diamond coatings. This work is focussed on the application of abrasive water jet cutting for machining these wear resistant MMCs. Cutting tests were performed at MMC-specimens with thickness of 2 - 25 mm. Experimental results are presented which clearly indicate the high potential and efficiency of the abrasive water jet for machining MMCs.