Market economy has become today the predominant economic system in the world. One of the tasks of the book is to define analytically the essential features of a market economy. The other purpose is to investigate the very working of a market economy which rests on firms defined as organizations and markets seen as institutions. It also supposes a renewed conception of cooperation and competition. The book will permit the reader to acquire a fresh view on market economies, stressing simultaneously their unity and diversity. It will also interest specialists of microeconomics as well as industrial organization, economics of technology and institutional economcis.