This volume provides a practical guide to building and using simulation models for international trade theory and policy. Through a sequence of carefully constructed and fully documented programs, the volume illustrates how GAMS can be used to analyze a wide array of problems. Modern computable general equilibrium (CGE) models for trade policy are challenging in their complexity, but can be thought of as constructions of much simpler building blocks. By developing the building blocks in a consistent manner, and then putting them together in more complex and interesting ways, the volume makes CGE accessible to anyone with a background in microeconomics/​trade theory.