With more than 169 geologically active volcanoes, the United States is among the most volcanically active countries in the world. During the twentieth century, volcanic eruptions have caused substantial economic and societal disruptions. Hazardous volcanic activity will continue to occur in the U.S., and, because of rising populations, development pressures, and expanding national and international air traffic over volcanic regions, risks to life and property through exposure to volcano hazards continue to increase. Moreover, rapid globalization makes U.S. businesses, financial markets, and government interests vulnerable to volcano hazards throughout the world.The mission of the U.S. Geological Survey (USGS) Volcano Hazards Program (VHP) under the Disaster Relief Act (P.L. 93-288) is to enhance public safety and reduce losses from volcanic events through effective forecasts and warnings of volcanic hazards based on the best possible scientific information. The VHP conducts four major science activities to reduce volcanic risk in the Nation: (1) monitoring volcano unrest and eruption, (2) preparing volcano hazard assessments, (3) conducting research on volcanic processes, and (4) providing reliable forecasts, warnings, and volcano-hazard information. These activities address the U.S. Department of the Interior's (DOI) Serving Communities strategic goal of protecting lives, resources, and property by making information available to communities to use in developing volcano hazard mitigation, preparedness, and avoidance plans, and support the Geology Strategic Plan (2001-2010) goals of conducting geologic hazards assessments for mitigation planning and providing short-term prediction of geologic disasters and rapidly characterize their effects.The VHP was reviewed in 2003 as part of the overall Geologic Hazards Program for the purpose of implementing the Program Assessment Rating Tool (PART). The Office of Management and Budget (OMB) found that the VHP role is clearly defined and unique from other Federal, State, local, or private entities. Three intermediate outcome measures are now tracked in support of the intermediate outcome of providing information to assist communities in managing risks from natural hazards. These outcome measures are (1) use rate of products, (2) percent of at-risk communities served with DOI science on hazard mitigation, and (3) adequacy of information. Output measures for which targets are now established in support of achieving the intermediate outcome goal include (1) maintenance of one hazard monitoring network, (2) delivery of risk assessments to customers, (3) presentation of formal workshops or training to customers, and (4) expanding the number of sites (mobile or fixed) monitored for ground deformation to identify volcanic activity.To address the growing national risk from volcanic activity, the VHP must monitor all hazardous U.S. volcanoes in real time so that data can be acquired, processed, interpreted, and disseminated rapidly. In the past decade, with new funding from Congress, the VHP and partners have built new monitoring networks in Alaska and expanded existing networks in Hawaii, Long Valley caldera, California, and Yellowstone's enormous volcanic system. However, significant gaps and deficiencies in monitoring capability remain at numerous, hazardous volcanoes, and nineteen volcanoes that pose a significant threat to air traffic completely lack the ground sensors necessary for basic monitoring. Furthermore, monitoring sensors currently deployed are becoming outdated, and many dangerous volcanoes are only monitored at a minimal level with regional networks of sparsely spaced seismometers. Consequently, the VHP must deploy adequate monitoring equipment when a volcano exhibits signs of significant activity, and scientists and civil authorities are placed in the position of "playing catch up" as a volcano's unrest increases, with scientists trying to install instruments and civil authorities struggling to develop and implement civil-defense measures before the situation worsens. Inevitably, this manner of response results in failing to monitor the early stages of volcanic unrest, which provide crucial, timely information needed to forecast the behavior of the volcano.The Office of Management and Budget (OMB) evaluated VHP in 2003 to establish the use of PART to track program performance. The OMB found that the VHP role is clearly defined and unique from other Federal, State, local, or private entities. As a result of the PART evaluation, three intermediate outcome measures and four intermediate output measures are now tracked in support of the intermediate outcome of providing information to assist communities in managing risks from natural hazards. Also, in the course of the evaluation, it was recommended that the VHP develop plans for a National Volcano Early Warning System (NVEWS) to prioritize and coordinate the future investment required for the Nation's volcano-monitoring infrastructure. As a first step, a report released in April 2005 assessed the relative threat posed by 169 geologically active volcanic centers within the United States and summarized a gap analysis of the monitoring level at each volcanic center in light of the threat assessment.