Waste prevention policies aim to reduce waste at the source and through reuse. So far, they focus primarily on single stages of the cycle of materials or on single types of waste. These policies reflect the reality that environmental problems have emerged and been addressed individually as, for example, mine tailings from extraction, hazardous waste from manufacturing facilities, greenhouse gas emissions from power-generating plants, or municipal waste largely from products. Extended Producer/Product Responsibility begins to build policy on recognition of the product cycle. However, no single set of physical accounts now provides the basis for taking a strategic approach to waste prevention. With colleagues in four other countries, the World Resources Institute (WRI), based in the United States, is developing a system to account for the physical materials used by national economies3. The accounts provide a standard framework for tracking materials into, through, and out of economies at all stages of the cycle from extraction, processing and manufacturing to use, recapture, and discard. The intent is to use materials as the currency to help countries to track physical performance of economies as monetary accounts of inputs and outputs help track economic performance. The physical accounts have the potential to provide the big picture of resource flows needed to make strategic choices about where to focus prevention—on which materials and at which stages of the life cycle—and monitor progress.