Virtually every category of food substance contains, either naturally or through contamination, trace levels of carcinogens. Whether they are traditional foods like grains, cheese, or mushrooms, spices like pepper or nutmeg, migrants from packaging materials, residues from pesticides or animal drugs, or unavoidable impurities from additives in processed foods; it is impossible to purge them completely. As our awareness of the ubiquity of carcinogens has grown, there has been a growing need to distinguish between tolerable and intolerable risk from carcinogens in food. This distinction — which relies inter alia on the toxicological principle of dose-response, the essence of quantitative risk assessment — is now regarded as crucial in the regulation of carcinogens,as it has been in the regulation of non-carcinogens. As suggested above this was not always so. Early FDA policy statements and the food safety laws themselves contained the implied promise of absolute safety from carcinogens in food. To understand the current role of carcinogen risk assessment in food safety policy, its relatively slow development, its conservative application, and the legal difficulties that still bar its wider use, it will be helpful to review some of the history of the food laws in the U.S.