This supplement introduces a CDC initiative to monitor and report periodically on the use of a set of selected clinical preventive services in the U.S. adult population in the context of recent national initiatives to improve access to and use of such services. Increasing the use of these services has the potential to lead to substantial reductions in the burden of illness, death, and disability and to lower treatment costs. The majority of clinical preventive services are provided by the health-care sector, and public health agencies play important roles in helping to support increases in the use of these services (e.g., by identifying and implementing policies that are effective in increasing use of the services and by collaborating with stakeholders to conduct programs to improve use). Recent health reform initiatives, including efforts to increase the accessibility and affordability of preventive services, fund community prevention programs, and improve the use of health information technologies, offer opportunities to enhance use of preventive services. This supplement provides baseline information on a set of selected clinical preventive services before implementation of these recent reforms and discusses opportunities to increase the use of such services. This information can help public health practitioners collaborate with other stakeholders that have key roles to play in improving public health (e.g., employers, health plans, health professionals, and voluntary associations), understand the potential benefits of the recommended services, address the problem of underuse, and identify opportunities to apply effective strategies to improve use and foster accountability among stakeholders.