Over the past several years, federal and state policymakers have considered a variety of proposals to increase health insurance coverage among the nation’s residents. Estimating the effects of those proposals on the size of the uninsured population, the cost of health insurance premiums, and the federal budget is a significant challenge. This background paper describes a model the Congressional Budget Office developed to simulate and analyze an array of policy options involving health insurance coverage. It describes the model’s design, basic methodology, and fundamental assumptions. To illustrate the model’s use, the paper reports estimates for two scenarios in which policy regarding health insurance coverage would differ from current law. In keeping with CBO’s mandate to provide objective, impartial analysis, the paper makes no recommendations.