The aging behavior of SiC particle reinforced 6061 aluminum matrix composites was investigated with Brinell hardness measurement, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For 40 vol%SiCp/6061Al composite, the age-hardening efficiency was lower than that of monolithic 6061Al alloy and its high strength was mainly attributed to the introduction of high volume fraction particles. At low aging temperature, the aging process of composite was more accelerated than that of 6061Al alloy. With temperature increasing, the time to reach the peak hardness was shortened and the precipitation processes became accelerated. Moreover, precipitation process observed in the matrix alloy was altered by the addition of SiC particles. Formation of G. P. region was severely suppressed and the activation energy of beta' phase decreased, which made the precipitation of beta' phase easier than that of 6061Al alloy. (C) 2004 Kluwer Academic Publishers.