The federal health center program, authorized in Section 330 of the Public Health Service Act, awards grants to support health centers: outpatient primary care facilities that provide care to primarily low-income individuals. The program-administered by the Health Resources and Services Administration (HRSA) within the Department of Health and Human Services (HHS)-supports four types of health centers: (1) community health centers; (2) health centers for the homeless; (3) health centers for residents of public housing; and (4) migrant health centers. According to HRSA data, there are over 8,633 unique health center sites (i.e., unique health center facility locations). Facilities must meet a number of requirements to receive a Section 330 grant, but receiving these grants enables health centers to receive services or in-kind benefits from a number of federal programs. Appropriations for the health center program have increased over the past decade, resulting in more centers and more patients served. From FY2000 through FY2012 the health center program's appropriation increased by 48%. Over this same time period, the number of health center sites increased by 59%. The program also received supplemental appropriations through the American Recovery and Reinvestment Act (P.L. 111-5) in FY2009. The program's expansion may continue under the Patient Protection and Affordable Care Act of 2010 (P.L. 111-148, ACA), which permanently authorized the health center program and created the Community Health Center Fund (CHCF) that included a total of $9.5 billion for health center operations to be appropriated in FY2011 through FY2015. However, it is not clear whether these funds will be used to expand the health center program because in FY2011, FY2012, and the FY2013 President's Budget request, these funds were or would be used to augment discretionary appropriation reductions to the health center program. Health centers are required to provide health care to all individuals regardless of their ability to pay and are required to be located in geographic areas that have few health care providers. These requirements make health centers part of the health safety net-providers that serve the uninsured, the underserved, or those enrolled in Medicaid. Data compiled by HRSA demonstrate that health centers serve the intended safety net population as the majority of patients are uninsured or enrolled in Medicaid. Some research also suggests that health centers are a cost effective way of meeting this population's health needs because researchers have found that patients seen at health centers have lower health care costs than those served in other settings. In general, research has found that health centers, among other outcomes, improve health, reduce costs, and provide access to health care for populations that may otherwise not obtain health care. This report provides an overview of the federal health center program including its statutory authority, program requirements, and appropriation levels. The report then describes health centers in general, where they are located, their patient population, and some outcomes associated with health center use. It also describes some federal programs available to assist health center operations including the federally qualified health center (FQHC) designation for Medicare and Medicaid payments. The report then concludes with a brief discussion of issues for Congress such as the potential effects of the ACA on health centers, the health center workforce, and financial considerations for health centers in the context of changing federal and state budgets. Finally, the report has two appendixes that describe (1) FQHC payments for Medicare and Medicaid beneficiaries served at health centers; and (2) programs that are similar to health centers but not authorized in Section 330 of the PHSA.