The discussion of policy needs focuses on what policy needs can be served by prevalence estimates, how prevalence estimation has been used for policy decisions, how prevalence estimation should be used for resource allocation, whether estimation efforts should emphasize prevalence at the national or local level, and the degree of accuracy necessary for policymakers. The examination of prevalence definitions considers the types of prevalence that should be estimated and the categories of user populations commonly estimated. The discussion of data sources examines the data sources currently available for prevalence estimation, the available data sources best suited for prevalence estimation, the characteristics of the "ideal" data set for prevalence estimation, improvement in current data systems to better support prevalence estimation, and improvement in access to these data to facilitate research. The discussion of estimation techniques first outlines the techniques that are available and their data requirements, followed by consideration of criteria for choosing among the estimation techniques, assessment of estimation results, validation of a prevalence estimation model, and why multiple methods should be used.