In situ observations of specimen surfaces have been used to characterize the fracture behaviour of particulate-reinforced metal-matrix composites. Composites of silicon carbide particle sizes 3, 10 and 30 mu m with volume fractions of 5, 10 and 20% in commercial-purity aluminium and aluminium-1% magnesium matrices were studied. The results of this surface study are compared with complementary metallographic studies of sectioned specimens illustrating behaviour from the bulk. Significant differences between the results of these two studies are outlined. Previous work using these techniques is critically examined and recommendations made for the appropriate interpretation of in situ straining experiments.