Learning ObjectivesContrast acute chlorine events, as assessed in 16 states during the years 1993-2000, with non-chlorine events with regard to the frequency of injury and the need for evacuation and decontamination.Recall whether and how chlorine exposures changed in frequency during the period under review, as well as the seasonal occurrence of events, the most common causes, symptoms of victims, and the use of protective equipment.Identify possible measures that could be taken in attempting to prevent chlorine-related injuries.Chlorine, a commonly used hazardous substance, can be harmful to human health when improperly released. Data from the Agency for Toxic Substances and Disease Registry’s Hazardous Substances Emergency Events Surveillance system were used to conduct a retrospective analysis on the public health consequences from acute chlorine releases in 16 states during 1993 through 2000. There was an overall decline in the number of chlorine events during the period analyzed; however, chlorine events were more likely to result in events with victims, evacuations, and decontaminations when compared with nonchlorine events (relative risk [RR] = 4.5, 95% confidence interval [CI] = 4.1 to 5.0; [RR] = 4.8, CI 4.3 to 5.3; and [RR] = 2.0, CI 1.7 to 2.4, respectively). Most chlorine victims were employees and members of the general public. The predominant symptoms sustained were respiratory and eye irritation. Equipment failure and human error were the most frequent factors leading to an event. Continuous employee training and preventive equipment maintenance can help prevent chlorine releases from occurring and minimize exposure to the general public.