The initiation and development of damage inside a 6061 Al alloy reinforced with SiC particles has been studied during in situ mechanical tests using high resolution synchrotron X-ray tomography. The high coherence of the X-ray beam used improves the detection of reinforcements in the matrix as well as the detection of cracks. Qualitatively, the same damage mechanisms are observed at the surface and in the bulk of the sample, the rupture of the SiC particles being the dominant mechanism for the early stages of plastic deformation. Quantitatively, however, it is found that the geometrical characteristics of surface SiC particles differ from those of bulk particles and that the damage growth rate is larger inside the sample. This result can be understood in terms of elastic energy and normal stress levels in the SiC particles as calculated by finite element method (FEM) analysis.