||The low-cycle fatigue behaviour of a cast metal matrix composite has been studied experimentally and numerically. Tensioncompression cyclic tests have been carried out in situ in a scanning electron microscope to observe damage mechanisms of a AS10U3NG alloy based composite reinforced with 10 vol.% SiCp. Micro-cracks always initiate on the specimen surface, on the biggest casting defects. Then the small cracks mainly propagate in the eutectic zone by precipitate fractures or by either particle/dendrite or particle/precipitate debondings. One of these cracks becomes the main crack. When the main crack reaches a critical length, it tends to grow in mode I through the dendrites and by particle fracture in front of the crack. As far as the numerical study is concerned, a finite element analysis models the composite behaviour under tensioncompression cyclic loading, before crack initiation, until a stabilised cycle is reached. Numerical and experimental stressstrain hysteresis loops are compared. Numerical and experimental cyclic stressstrain curves are in a good agreement.