The metal matrix composite materials consist of 10, 15 and 20 vol.% alumina particles in an aluminium alloy 6061-T6 matrix. Specimens were taken from hot-extruded rods and the tensile tests were carried out at various strain rates. High strain rate tests were performed by the split-Hopkinson-bar method. The fracture surfaces were observed with a scanning electron microscope to understand the fracture mechanisms. From the results, it can be concluded that: (1) the alumina-reinforced composites are more sensitive to strain rate than the unreinforced material, (2) the strain rate sensitivity of the ultimate tensile strength of these composites increases with increasing temperature and (3) the addition of alumina particles will reduced the ductility of aluminium alloy 6061-T6, irrespective of the strain rate and temperature.