Society makes some of its greatest demands on the science and technology of materials through its huge and growing requirements for energy. With reserves of oil and natural gas beginning to look quite inadequate to meet world needs beyond the next ten years or so; with concern for the environment becoming an increasingly important factor in industrial and social policy-making; and with most countries now pinning their faith on nuclear power to solve their future energy problems; with all these the energy industry is faced with vast and challenging problems, the solution of many of which can come only through the development of new or improved materials. The conditions under which materials are expected to operate in power plant are becoming increasingly severe, as temperatures, stresses, chemical and—in nuclear reactors—radiation attacks are raised to higher levels of intensity, in the struggle for greater outputs and higher efficiencies. Difficulties with materials have blocked the development for large-scale usage of several new types of power plant, although advances in superconducting materials have opened new possibilities in other directions. There is a great and growing need for better materials for catalysts; a major breakthrough here could bring big social benefits.