"Some issues that influence the implementation of Ceramic (CMC) and titanium (TMC) matrix composites in high-temperature systems are addressed. Commonalities and differences are brought out by comparing and contrasting their themomechanical characteristics, with examples. Emphasis is given to the role of design and the use of mechanism-based models of material behavior. Factors addressed include the relative significance of thoughness and ductility for thermostructural applications, including their manifestation in the notch sensitivity. The detriments caused by anisotropy are examined, through discussions of mechanisms such as delamination in CMC's and transverse debonding in TMC's."--Page 1.