The article by Peter Barss is a valuable contribution to the existing literature on the investigation of the use of chemical, biological, or toxin weapons (CBW).1 He constructs detailed procedures to investigate allegations of the use of any of these weapons from the perspective of epidemiology theory. Barss reviews the investigations of the alleged use of toxin weapons (“yellow rain”) in Laos and Cambodia, the use of chemical weapons by both sides in the Iran-Iraq war, and the use of chemical weapons by Iraq against its own Kurdish population. He argues persuasively that these inquiries would have been conducted more effectively if the teams had followed standard procedures for field investigations according to epidemiology theory.