Recent scientific developments are changing knowledge about risks in the food supply and revolutionizing procedures for controlling those risks. New tests reveal that micro-organisms are a more common cause of foodborne disease than most Americans suspect. New data on widely used chemicals sometimes show levels of residues so low that they were formerly undetectable. Rapid tests may improve monitoring of the critical control points in food production and distribution. The improved testing could trigger legal restrictions. Many food safety policies were adopted before these testing improvements. The challenge is to incorporate this new knowledge into workable food safety policies that take into account the economic costs and benefits of such regulation.