Governments may perform health technology assessment (HTA) in their roles as a regulator in the public interest, as a source of information for decision makers in the public and private sectors, and/or as a purchaser or provider of healthcare services. The U.S. government's roles in the health sector as a regulator, source of information, and purchaser and provider of services are influenced both by characteristics of that sector and by its stakeholders' effectiveness in influencing national health policy debates.