Exposure to agents that cause cancer and other diseases occurs in everyday life and particularly in certain workplace settings. In an urban environment everyone is exposed to smog and other air pollutants in addition to natural background radiation and solar ultraviolet light. An estimated 50 million people currently smoke in the U.S. Millions more experience the irritating effects of secondhand (environmental tobacco) smoke. 1 Some agents we are exposed to are known or suspected human carcinogens. How should the collective impact of these agents be evaluated? Analyzing the health impact of a single agent without regard to the presence of competing risks is inappropriate because perspectives on isolated risks can be distorted easily. Agents may interact in ways that enhance or diminish risk. The logical approach to dealing with multiagent exposures is to express health impacts for each agent in terms of a common currency — risk. Ideally health protection frameworks for carcinogens should be coherent. In principle a set of common assessment and management concepts and tools can be developed by using a risk-based system that may be applied to a broad array of agents.