Summary: The Community and Migrant Health Center program and the National Health Service Corps, administered by the federal Health Resources and Services Administration (HRSA), are designed, respectively, to increase the availability of primary and preventive health care services for low-income people living in medically underserved areas and to offer scholarships and educational loan repayments for health care professionals, some of whom, in turn, agree to work in these centers. GAO found that HRSA could increase the centers' effectiveness by establishing a systematic best practices program for their learning and by improving the completeness and accuracy of the data its uses to monitor them. Also, the Health Care Financing Administration could help ensure the centers' ability to continue serving Medicaid beneficiaries and uninsured persons by monitoring state Medicaid programs' compliance with federal requirements for reimbursing the centers. Shifting resources would help provide more National Health Service Corps loan repayments, and a better system is needed for identifying and measuring where health care professional placements are needed.