The influence of test temperature on the mechanical and fracture properties of a 20 vol% alumina particulate-reinforced 6061 -aluminium matrix composite, in the peak-aged condition, was investigated in the temperature range 25-180-degrees-C. Strength and stiffness were found to decrease but elongation to failure increased with increasing test temperature. However, the fracture toughness was relatively constant over this temperature range. The failure mechanism, the reaction zone around reinforcing particles, the number of debonded particles and void sizes were all significantly influenced by temperature. The role of the matrix/particle interface in the fracture process was also investigated.