H activities have degraded many of the world’s ecosystems, which has created an urgent need for strategies that can restore their ecological integrity. This need is accompanied by many scientific challenges, however. In particular, ecosystems are among the most complex entities in the hierarchy of life, and the successful repair of damaged systems will require a deep understanding of the processes that determine their structure and function. Biologists have a critical role to play in creating this knowledge because of their expertise in such varied phenomena as the role of microbes in detoxifying anthropogenic contaminants, the effects of disturbance on population persistence, and the factors influencing competitive interactions between native and exotic species. By itself, however, biological knowledge is not sufficient for restoring degraded ecosystems. Two other types of expertise are also needed for developing integrated restoration solutions. First, because ecosystems are composed of many interacting abiotic and biotic components, biologists must collaborate with their colleagues in the physical sciences to learn how these systems work. Second, because humans are such strong interactors in these complex systems, we need to work with experts who can help us understand how human attitudes, institutions, and technologies influence the condition and management of ecosystems. Such enhanced interdisciplinary dialogue and unified approaches are essential for creating public policies that can sustain the planet’s life support systems (Lubchenco 1998, Covich 2000, Ludwig et al. 2001). Proposals to restore rivers via dam removal raise many issues that require broad discussion and teamwork. This approach to river restoration derives from the growing recognition that dams often disrupt the structure and function of river ecosystems by modifying flow regimes, disrupting sediment transport, altering water quality, and severing their biological continuity (Ward and Stanford 1979, Petts 1984, Collier et al. 1996). Future dam removal decisions can be enhanced by developing a more complete scientific understanding of the processes that determine how rivers are affected by different types of dams and how they respond to dam removal. There is an equally important need to understand the social, economic, engineering, and legal factors that influence dam removal decisions. Assembling a diverse array of experts to explore these different facets of dam removal was an exciting challenge for us. Listening to and participating in the dialogue that took place when those experts gathered at the annual meeting of the Ecological Society of America in August 2001 was even more rewarding. This special section of BioScience brings together those diverse authorities, and a few others, to examine the potential utility of dam removal as a method of river restoration. Our goal is not just to explore the many different scientific and social aspects of this topic but also to consider how these components can and should be connected. Bruce Babbitt, former secretary of the US Department of the Interior during the Clinton administration, is intimately familiar with the subject matter, having been present—sledgehammer in hand— at many dam removals across the United States. His passionate essay (Babbitt 2002) clearly frames both the scientific and human dimensions of the subject. In particular, he emphasizes the critical need for strong science, not just to predict what will happen when dams are removed but also to monitor dam removal outcomes so that we learn how to maximize the effectiveness of this restoration method.