Public health threats from intentional releases of chemicals into the environment (ie, chemical terrorism) are an increasing concern in the United States. Recent situations of deliberate contamination of food and beverages with chemicals highlight the need for health care providers and public health officials to be alert for adult and pediatric patients in their communities who have signs and symptoms consistent with chemical exposures. In an effort to increase knowledge of surveillance and preparedness for illness related to potential chemical releases, we provide guidance to health care providers and public health personnel for recognizing illnesses or patterns of illnesses that might be associated with the intentional, covert release of chemical agents. In this article, we will discuss 5 examples of outbreaks of illnesses after a covert chemical release, obstacles to recognition of these illnesses, clues (ie, epidemiological patterns and syndromic presentations) that might enhance the recognition of illnesses from a covert chemical release, and public health strategies to enhance the rapid identification of a chemical terrorism event.