The Department of Health and Human Services (HHS) has designated 8 of its 11 operating divisions (agencies) as components of the U.S. Public Health Service (PHS). The PHS agencies are (1) the Agency for Healthcare Research and Quality (AHRQ), (2) the Agency for Toxic Substances and Disease Registry (ATSDR), (3) the Centers for Disease Control and Prevention (CDC), (4) the Food and Drug Administration (FDA), (5) the Health Resources and Services Administration (HRSA), (6) the Indian Health Service (IHS), (7) the National Institutes of Health (NIH), and (8) the Substance Abuse and Mental Health Services Administration (SAMHSA). While the PHS agencies all provide and support essential public health services, their specific missions vary. With the exception of FDA, the agencies have limited regulatory responsibilities. Two of them—NIH and AHRQ—are primarily research agencies. NIH conducts and supports basic, clinical, and translational medical research. AHRQ conducts and supports research on the quality and effectiveness of health care services and systems. Three of the agencies—IHS, HRSA, and SAMHSA—provide health care services or help support systems that deliver such services. IHS supports a health care delivery system for American Indians and Alaska Natives. Health services are provided directly by the IHS, as well as through tribally contracted and operated health programs, and through services purchased from private providers. HRSA funds programs and systems to improve access to health care among low-income populations, pregnant women and children, persons living with HIV/AIDS, rural and frontier populations, and others who are medically underserved. SAMHSA funds community-based mental health and substance abuse prevention and treatment services. CDC is a public health agency that develops and supports community-based and population-wide programs and systems to promote quality of life and prevent the leading causes of disease, injury, disability, and death. ATSDR, which is headed by the CDC director and included in the discussion of CDC in this report, is tasked with identifying potential public health effects from exposure to hazardous substances. Finally, FDA is primarily a regulatory agency, whose mission is to ensure the safety of foods, dietary supplements, and cosmetics, and the safety and effectiveness of drugs, vaccines, medical devices, and other health products. In 2009, Congress gave FDA the authority to regulate the manufacture, marketing, and distribution of tobacco products in order to protect public health. The programs and activities of five of the PHS agencies—AHRQ, CDC, HRSA, NIH, and SAMHSA—are mostly authorized under the Public Health Service Act (PHSA). While some of FDA's regulatory activities are also authorized under the PHSA, the agency and its programs derive most of their statutory authority from the Federal Food, Drug, and Cosmetic Act (FFDCA). HRSA's maternal and child health programs are authorized by the Social Security Act (SSA), and many of the IHS programs and services are authorized by the Indian Health Care Improvement Act. ATSDR was created by the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA, the "Superfund" law). The primary source of funding for each PHS agency is the discretionary budget authority it receives through the annual appropriations process. AHRQ, CDC, HRSA, NIH, and SAMHSA are funded by the Departments of Labor, Health and Human Services, and Education, and Related Agencies (LHHS) appropriations act. Funding for ATSDR and IHS is provided by the Department of the Interior, Environment, and Related Agencies (Interior/Environment) appropriations act. FDA gets its funding through the Agriculture, Rural Development, Food and Drug Administration, and Related Agencies (Agriculture) appropriations act. The annual LHHS appropriations act gives the HHS Secretary limited authority to transfer funds from one budget account to another within the department. The Secretary may transfer up to 1% of the funds in any given account. However, a recipient account may not be increased by more than 3%. Congressional appropriators must be notified in advance of any transfer. The HHS Secretary used this transfer authority in FY2013 and again in FY2014 as part of a broader effort to provide the Centers for Medicare & Medicaid Services (CMS) with additional funding to implement the Affordable Care Act (ACA). In FY2013, for example, NIH was the primary source of transfers both to CMS for ACA implementation and to CDC and SAMHSA to help offset a loss of funding for those two agencies from the ACA's Prevention and Public Health Fund (PPHF, discussed below). A significant portion of the FY2013 PPHF funds that were originally allocated to CDC and SAMHSA were reallocated to CMS, also for ACA implementation. In FY2014, NIH was again the primary source of transfers to CMS to support ACA implementation. In addition to the transfer authority provided in the annual LHHS appropriations act, Section 241 of the PHSA authorizes the HHS Secretary, with the approval of congressional appropriators, to use a portion of the funds appropriated for programs authorized by the PHSA to evaluate their implementation and effectiveness. This long-standing budgeting authority is known as the Public Health Service Evaluation Set-Aside (set-aside), or PHS budget "tap." Under this authority the appropriations of numerous HHS programs are subject to an assessment. Although the PHSA limits the set-aside to no more than 1% of program appropriations, in recent years the annual LHHS appropriations act has specified a higher amount. The FY2016 LHHS appropriations act capped the set-aside at 2.5%, the same percentage that has been in place since FY2010. Following passage of the annual LHHS appropriations act, the HHS Budget Office calculates the assessment on each of the donor agencies and offices. These funds are then transferred to various recipient agencies and offices within the department for evaluation and other specified purposes, based on the amounts specified in the appropriations act. Table 1 shows the total assessments and transfers for FY2013, by HHS agency and office, and indicates whether the entity was a net donor or recipient of set-aside funds that year. These figures are broadly representative of the distribution of set-aside funds that occurred each fiscal year over a period of several years prior to FY2015, when the appropriators decided to make major changes to the allocation of such funds. NIH, whose annual discretionary appropriation exceeds that of all the other PHS agencies combined, is subject to the largest assessment of set-aside funds. NIH contributed almost $710 million (69%) of the $1.026 billion in set-aside funds in FY2013. However, the agency received $8 million in set-aside funding, making it a significant net donor of set-aside funds. Similarly, HRSA contributed more set-aside funds than it received in FY2013. On the other hand, AHRQ, CDC, and SAMHSA were net recipients of set-aside funding in FY2013. The Administration for Children and Families (ACF) and various offices within the Office of the Secretary (OS) also received set-aside funds. Table 1 also shows the set-aside assessments and transfers for the current fiscal year (i.e., FY2016). These figures reflect the significant changes that the appropriators first made in FY2015 by returning most of the set-aside funding to NIH and eliminating any transfers to AHRQ, CDC, and HRSA. As a result, NIH has gone from being by far the largest net donor of set-aside funds to a net recipient of such funding. Meanwhile, AHRQ and CDC have experienced a significant loss of set-aside funding and are now both net donors of these funds. The situation with AHRQ is of particular interest to many. From FY2003 through FY2014, AHRQ did not receive an annual discretionary appropriation. The agency was supported by set-aside funds and, in recent years, by amounts from other sources. In FY2015, however, AHRQ received a discretionary appropriation for the first time in more than a decade in lieu of receiving any set-aside funding. That continues to be the case in FY2016. Although the bulk of PHS agency funding is provided through annual discretionary appropriations, agencies also receive mandatory funding, user fees, and third-party collections. As discussed below, these additional sources of funding are a substantial component of the budget of several PHS agencies. The ACA included numerous appropriations that together provided billions of dollars in mandatory spending to support specified grant programs and activities within HHS. A few PHS agencies continue to receive these funds, which are itemized in the funding tables in this report. The ACA also established and funded three multibillion dollar trust funds to help support PHS agency programs and activities. First, the ACA provided a total of $11 billion in annual appropriations over the five-year period FY2011-FY2015 to the Community Health Center Fund (CHCF) . These funds help support the federal health centers program and the National Health Service Corps (NHSC), both of which are administered by HRSA. The Medicare Access and CHIP Reauthorization Act of 2015 (MACRA) appropriated two more years of funding for the CHCF; a total of $3.910 billion for each of FY2016 and FY2017. A table summarizing each fiscal year's CHCF appropriation and the allocation of funds appears in Appendix A . Second, the Prevention and Public Health Fund (PPHF) , for which the ACA provided a permanent annual appropriation, is intended to support prevention, wellness, and other public health programs and activities.