Over the past five decades, metal matrix composites (MMCs) have been transformed from a topic of scientific interest to a material of technological and commercial significance. The worldwide MMC markets in 1999 accounted for 2500 metric tons valued at over $100M. MMC applications in ground transportation, thermal management, aerospace, industrial and recreation industries have been enabled by a range of attractive properties. Challenging technical issues have been overcome, including affordable primary and secondary processing, material design methodologies, and control of interfacial properties. This overview describes the technological features of the MMC industry. Primary and secondary commercial processes will be broadly described and metrics that underscore the growing maturity of the MMC industry will be discussed. MMC applications in the major markets will be described. Selected case studies will illustrate technology challenges that have been overcome and to highlight successful implementation strategies.