Composite materials are used in a very wide range of industrial applications. In this chapter, the objective is to identify some of the considerations involved in commercial exploitation of composites. This is done by means of a few case studies and there is no attempt to present a systematic survey. The examples given cover a range of composite type, engineering complexity, manufacturing route, market size and competitive position relative to conventional materials. At the beginning of each case study, a list is given identifying the reasons for preferring a composite to more conventional engineering materials. Although the examples are spread over the full range of matrix types, the bulk of the annual composite production of around 10 million tonnes is currently in the form of PMCs. At the start of each example, a list is given of the requirements of the application.