the reinforcement of metal matrices by long ceramic fibers such as alumina, carbon, silicium carbide, leads to very high specific characteristics such as stiffness and strength at both room and high temperature. progress achieved in the development of new fibers performance has revived the interest for metal matrix composites (mmc) development. after having briefly reviewed the basic laws of unidirectional composites linear mechanics and shed some light on the major role played by fiber-matrix interface in the micromechanics and behavior of these materials, their processing techniques and characteristics are examined. the improvement of the mechanical characteristics of the new generation of composites arises not only from the fiber surface treatment leading to a control of fiber matrix bond strength, but also to the processing techniques derived either from casting or rapid solidification rate techniques. mechanical characteristics of the most relevant mmc are presented for both metallic and intermetallic matrices. attention is drawn to particular behavior such as thermal expansion, thermal cycling, and corrosion resistance