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 release 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.