rT HE analysis of problems of monopolistic competition has reached a stage in which any further progress is seriously hampered by the lack of a systematic consolidation of the many divergent theories, which have marked the development of the centuryold controversy. More than in any other field of economic theory, the real issue is that of selecting an appropriate set of fundamental assumptions. The validity of the most ingenious argument might be easily endangered by unconscious introduction of unstated premises. It would be naive to expect that, in attacking a new problem, the theorist should beforehand present a complete and closed list of assumptions; the selection of most appropriate premises can be obtained only through a long process of trial and error. On the other hand, however, no deductive argument deserves the name of a theory unless it has undergone the strictest possible test of logical consistency. The simplest and most efficient way to perform this test is that of retracing the whole argument on the basis of the final, definitive set of assumptions. In the case of quantitative theory, a mathematical reformulation of it appears to be particularly appropriate. In Marktform und Gleichgewicht, Heinrich von Stackelberg performs the difficult task of strictly deductive reformulation of the theory of monopolistic competition with much skill and elegance. Four of the six chapters of this book are devoted to systematic exposition of the fundamental theory; chapter v gives a critical survey of its development from Cournot up to Mrs. Robinson and Chamberlin; chapter vi deals with questions of market disequilibrium as object of economic policies. The mathematical groundwork of the theoretical discussion is presented separately in a large Appendix. The main lines of the argument are developed here with the help of elementary calculus and are further clarified through a number of numerical examples. Although no mathematical formulas are used in the main part of the text, the strong analytical foundation is discernible throughout the whole book.