The study was performed in the context of a field training exercise for response to deployment of a chemical weapon against a civilian population in St. Louis, MO, in May 2002. Sodium fluorescein was selected as a chemical surrogate for this investigation. The features of this chemical surrogate that make it a desirable test agent for this assessment include solubility in water, thus enabling it to mimic many of the caustic or corrosive agents that may be used in an actual event. It is only poorly visible in natural or room lighting, so victims are not aware of specific locations on their person where contamination may remain; however, it fluoresces readily in the presence of black ultraviolet light. The chemical surrogate that remained after decontamination was assessed with ultraviolet light. The water solution of the sodium fluorescein was applied to 10 volunteer victims and their clothing with a spray bottle before they were positioned at the scene of the purported release. Fire department hazardous materials specialists set up an outdoor chemical decontamination corridor according to generally recognized methodologies. The scanning of clothing collected as evidence showed that residual contamination remained on the pants from each of the 10 victims. No contamination was identified on the skin of victims at the scene following the gross decontamination procedure. Because victim clothing remained contaminated in this study, handling it posed significant potential for hazard to persons who conducted forensic investigation of such items after an event. It is prudent for each jurisdiction to assess its procedures for victim decontamination and evidence collection and consider evidence seized from victims in a chemical event to be contaminated until definitively proven otherwise. Jurisdictions should plan for secondary containment of evidence bags and to work with response staff from the FBI in managing the collection and storage of these items in an event. One table shows the incubation period, lethality, persistence, and dissemination of various bacterial, viral, and biological toxins, and another table shows the signs and symptoms, decontamination periods, and persistence of various chemical agents.