This paper discusses the use of composite plastic materials in the manufacture of wind turbine blades. An overview of the design requirements of wind turbine blades is followed by an explanation of how composite materials can meet these requirements. Current manufacturing processes are explained, followed by recent advances and future developments in a number of areas. Advances in materials are discussed, followed by design and manufacture developments. The use of composite materials to deal with maintenance and reliability issues is discussed. Finally, developments in multi-section and modular blades is discussed. A number of approaches from different manufactures are discussed and a number of patents are looked at. Developments in each of these areas are required to meet this demand, but there is no consensus from manufacturers on the best way forward.