"Macroeconomic Theory", in its first edition, was widely adopted for use as a graduate text; this updated and expanded version should find even greater popularity as a text and as a research reference. It has been substantially revised to include three entirely new chapters: The Consumption Function, Government Debt and Taxes, and Dynamic Optimal Taxation. Significant additions have been made to three of the original chapters dealing with difference equations, stochastic difference equations, and investment under uncertainty.