Chapter 20. Solution Software for Computable General Equilibrium Modeling We describe the progress of computable general equilibrium (CGE) modeling software since the 1980s and contrast the main systems used today: GAMS MPSGE and GEMPACK. The development of these general purpose modeling systems has underpinned rapid growth in the use of CGE models and allowed models to be shared and their results replicated. We show how a very simple model may be implemented and solved in all three systems. We note that they produce the same numerical results but have different strengths. We conclude by considering some challenges for the future.