In the past decades, the incorporation of ceramic reinforcement in metal-matrix composites (MMC’s) brought about considerable improvements in elastic modulus, strength, wear resistance, structural efficiency, reliability and control of physical properties (e.g. density and coefficient of thermal expansion) thereby providing for improved mechanical performance in comparison to the unreinforced matrix [1–4]. S-N curves for materials such as steels are available elsewhere [5–6] whereas are limited for MMC’s. Studies on the elastic constants behavior for MMC’s as a function of temperature, volume fractions of reinforcement and applied stresses had already been conducted [7–8]. However, the fatigue behavior of elastic constants in MMC’s is not well understood. Further, the trend now is aimed at nondestructive evaluation (NDE) of materials which in the past years gained significant attention over the conventional destructive tests since the former is capable of determining the usefulness, serviceability or quality of a part or material without limiting its usefulness, which is not possible in the latter’s case [9–10]. In view of the above discussion, a result of the study on the fatigue behavior and ultrasonic characterization of monolithic aluminum and aluminum MMC’s will be discussed here.