Ceramic-reinforced aluminum alloys exhibit a unique combination of properties not found in monolithic aluminum alloys. The addition of high modulus ceramic particles to conventional aluminum alloys results in increased strength, elastic modulus, and wear resistance. Because of these desirable engineering properties, the damping capacity and storage modulus were measured as a function of ceramic volume fraction, temperature, and frequency. Two aluminum-silicon-magnesium matrix composites were studied including the wrought alloy, 6061-T6, with 0 to 0.2 volume fraction of Al2O3 particles and the casting alloy, A356-T6, with 0 to 0.2 volume fraction of silicon-carbide (SiC) particles. They were manufactured by a process that is simpler and less costly than previously developed techniques for manufacturing metal matrix composites. The damping capacity and storage modulus were measured at 0.1, 1, and 10 Hz, while the temperature was varied from — 10 to 250°C. It was found that the cast matrix has a higher damping capacity than the wrought matrix above 100°C, possibly due to the presence of silicon in the matrix that lowers the grain boundary transition peak. The storage modulus and damping capacity increased with increasing reinforcement content. These results are consistent with other work done on ceramic-reinforced aluminum alloys.