This text explains the way in which information and knowledge are treated in contemporary economic theories and, therefore, contributes to our understanding of the importance of the strategic organization of information and the acquisition of know-how to the behaviour of modern economies. It gathers together contributions of experts on the role of information in the various theories covered: specifically, in system analysis, in game theory, in the statistical theory of information , in theories of market pricing, of financial speculation and of bounded-rationality decision making, in the evolutionary theory of the firm, in the new industrial economics and in the economics of codification . The text is divided into three parts. Part one deals with general theories of information. Part two addresses the role of information in the functioning of markets. Part three considers the importance of information to the operation of organizations. Conclusions are drawn in part four on the implications for the process of economic growth and for economic policies.