The dynamic mechanical properties of polymethyl methacrylate reinforced with different amounts of aluminum filler were investigated. The internal friction and the shear storage modulus were measured with an automated damped torsional pendulum in the temperature range between 200 and 375 Kin an argon atmosphere. An increase in the glass transition temperature occurred at higher filler contents. The amount of filler in the matrix seems to modify the beta relaxation of the composite. The dynamic modulus increases with the aluminum percentages for low filler content. These results were explained in terms of a model presented in the literature for the elastic modulus.