This book presents the contributions of the 20th century to economic theory in a mathematical language and in historical sequence. General equilibrium is the focal point of the book; but also a number of macroeconomic models, especially with respect to the first half of the century, are considered. Dynamic models are extensively studied per se, and not merely as extensions of their static counterparts. The book with its extensive bibliography gives a broad view over the developments in mathematical economics and is therefore an invaluable source of information for researchers and students working in this field.