The Committee on Environment and Natural Resources (CENR) consists of seven issue subcommittees and three cross-cutting subcommitees--Risk Assessment, Social & Economic Sciences, and Environmental Technology. While this strategy for the Subcommittee on Toxic Substances and Hazardous and Solid Waste is presented within a risk assessment and risk management framework, it identifies research needs for evaluating and managing risks associated particularly with toxic substances and wastes. In contrast, the strategy of the Subcommittee on Risk Assessment addresses methodological research needs for evaluating a range of environmental hazards, including not only toxic materials but also the problems addressed by other CENR subcommittees (e.g., global change, natural hazards, air quality, water resources, and the loss of biodiversity).