The disappointing degree of market penetration for monolithic engineering ceramics is due to a combination of economic factors and the reluctance to apply statistical failure criteria to critical components with fracture toughness values generally below 10MPam1=2. The concept of damage-tolerance using long fibres in ceramic matrix composites (CMCs) was demonstrated in the 1970s, following the evolution of high-strength carbon fibres. Further development of ceramic matrix composites was promoted by the availability of polymer-precursor fibres based on SiC (Nicalon and Tyranno) and the fortuitous in situ formation of carbon-rich debond interfaces within silicate matrices. This precipated the successful theoretical modelling of mechanical behaviour in parallel with experiments on SiC/silicate and chemical vapour infiltrated SiC/SiC systems. This chapter presents a brief survey of the key microstructural parameters required for ideal ceramic matrix composite performance and highlights some of the technical and microstructural problems which inhibit engineering application. Current potential for applications in industrial gas turbines is discussed in chapter 5.