Sintering temperature is one of the critical parameters in the sintering of composites. It was found that the density of a sintered metal matrix composite compact at relatively lower sintering temperature could only be slightly changed. Although compaction of the matrix metal (Al-4.5wt.%Cu) could be densified from an original 70% to 96% of its theoretical density by liquid phase sintering (LPS), density of a composite compact could not be increased at the same sintering temperature. The composite compacts could be densified up to only about 91% of their theoretical density if 21.6% of liquid phase sintering was employed. The temperature employed was much higher than that used in the liquid phase sintering of its base metal. K-IC measurement of the compacts revealed an increase of about 50% if high temperature sintering was used. Fracture surface analysis showed an incompletely sintered structure due mainly to high viscosity of the sintered particles. It is, therefore, suggested that the temperature for sintering metal matrix composites should be increased in order to lower the viscosity. A simple model is here proposed to predict the amount of the liquid phase needed whereby the sintering temperature can be chosen accordingly.