Past Global Changes (PAGES) is a worldwide program that seeks to facilitate international and interdisciplinary collaborations aimed at understanding the Earth's past environment to make sound predictions for the future. PAGES' scope of interest includes the physical climate system, biogeochemical cycles, ecosystem processes, biodiversity, and human dimensions. PAGES is a core project of the International Geosphere-Biosphere Programme (IGBP) and is funded by the U.S. National Science Foundation, the National Oceanic and Atmospheric Administration, and the Swiss National Science Foundation. PAGES is overseen by a Scientific Steering Committee comprised of members chosen to provide a range of scientific expertise and a balance of nationalities. It is run by a small International Project Office that serves as a critical interface between scientists and science initiatives. The Office manages projects; organizes and supports meetings and courses; aids in synthesizing research results in collaboration with scientists at large; publishes a free, international science newsletter; and provides and maintains a Web site that offers a variety of additional services. PAGES has over 3000 member scientists in more than 100 countries around the world. Membership is free and open to anyone. The PAGES Web site, www.pages-igbp.org, receives over 1500 hits a day.