This study addresses the need for dynamic mechanical properties of advanced materials which are available only in small quantities by evaluating the ability of the Piezoelectric Ultrasonic Composite Oscillator Technique (PUCOT) to measure the dynamic modulus of small specimens of fibrous and particulate metal matrix composites. This is accomplished by measuring the dynamic modulus of several small rod or bar-shaped specimens of 6061 aluminum reinforced with silicon carbide fibers or particles (Al/SiC) at room temperature with the PUCOT. The fiber or particle volume fractions of the Al/SiC specimens vary from 8 to 56 percent and void volume fractions range from zero to 15 percent. The results are examined in terms of the dynamic modulus and specific dynamic modulus as a function of reinforcement volume fraction. Experimental results show that the modulus versus volume fraction for the fiber-reinforced composites deviates from the linear rule-of-mixtures due to the presence of voids and fiber damage. For the particulate composites, the modulus values fall within the bounds predicted by variational principles. A “strength of materials” approximation based on the assumption of cubic particles has limited success in predicting the particulate composite data. The results demonstrate the ability of the PUCOT to measure accurately the dynamic modulus of small specimens with minimal specimen preparation.