To facilitate development of USDA’s annual 10-year agricultural projections, the Economic Research Service (ERS) maintains models of the agricultural sector of 44 major exporting and importing countries and regions, including the United States. These models, customized to the specific countries and regions, produce medium- to long-term projections of the supply and use of major agricultural commodities based on behavioral responses to world market prices, trade and domestic agricultural policies, and domestic commodity prices. ERS also uses the models for research on contemporary global or country-specific, agriculture-related issues. While the models, which together make up the Country-Commodity Linked System (CCLS), can be run in isolation, they also can be linked to simultaneously solve 24 commodity markets, obtaining equilibrium world prices and balanced trade. To increase knowledge and understanding of the models, this report describes their underlying economic structure and provides an overview of the CCLS. It also presents an illustrative example of how the models were used to examine the impact on domestic and world markets of increasing crop yields in one region of the world.