In the spring of 2004, the U.S. Geological Survey (USGS) Menlo Park Center Council commissioned an interdisciplinary working group to develop a forward-looking science strategy for the USGS Menlo Park Science Center in California (hereafter also referred to as "the Center"). The Center has been the flagship research center for the USGS in the western United States for more than 50 years, and the Council recognizes that science priorities must be the primary consideration guiding critical decisions made about the future evolution of the Center. In developing this strategy, the working group consulted widely within the USGS and with external clients and collaborators, so that most stakeholders had an opportunity to influence the science goals and operational objectives. The Menlo Park Science Center is the largest USGS science center in the Western Region and has the greatest breadth of scientific capabilities. The Center is strategically located to take advantage of partnerships in one of the greatest geographic concentrations of nationally and internationally recognized Earth science institutions in the world. The Center also houses the most extensive laboratory, library, and other research-support infrastructure of any USGS facility in the West. USGS scientists in Menlo Park lead in implementing many national USGS science activities, as well as in supporting science activities at other USGS science centers throughout the region and the nation. Other, smaller USGS science centers in the Western Region are designed with more limited scientific and (or) geographic scopes to their programs. The economic, workforce, and scientific planning environment for the Menlo Park Science Center has changed rapidly over the past two decades. Staff size has decreased, and there has been a shift in emphasis from basic to applied research. Despite the high cost of living, the USGS attracts top scientists for research positions in Menlo Park, largely because of the Center's scientific reputation and setting within the vibrant research environment in the San Francisco Bay Area. Also attractive is the healthy employment market for spouses of USGS scientists in the Bay Area. A number of recent trends in society and science are important to consider for future science at the Menlo Park Science Center. These include rapid urban population growth, especially in coastal areas; globalization of resource development; increasing demand for limited water resources; global climate change; and increasing capability to construct predictive Earth-system models. The most promising science directions at the Menlo Park Science Center have evolved and will continue to evolve from traditional capabilities in geologic and hydrologic research, complemented by a growing capability in geographic research, and hopefully augmented by biological expertise from USGS biological resources programs. Future science in Menlo Park will build on and link existing strengths to lead research that supports USGS program priorities as they evolve to meet America's science needs throughout the region, the Nation, and the world. This science strategy recommends that the USGS Menlo Park Science Center continues to address important national science needs by focusing on Earth-system science through four equally important and interrelated Science Goals, each with associated strategic actions. These Science Goals are to: Natural Hazards: Conduct natural-hazard research and assessments critical to effective mitigation planning, short-term forecasting, and event response. Ecosystem Change: Develop a predictive understanding of ecosystem change that advances ecosystem restoration and adaptive management. Natural Resources: Advance the understanding of natural resources in a geologic, hydrologic, economic, environmental, and global context. Modeling Earth System Processes: Increase and improve capabilities for quantitative simulation, prediction, and assessment of Earth system processes.