The Hazardous Substances Emergency Events Surveillance (HSEES) system collected information on 9014 acute hazardous substance releases in 15 participating states in 2002. There were 3749 fixed-facility manufacturing events, of which 2100 involved "interruptions" to normal processing and 1649 "comparisons" that did not involve interruption. Equipment failure (69%) or intentional acts (20%) were the main root factor. Many events occurred in October and November in three states (Texas, Louisiana, and New Jersey), in three manufacturing industries (industrial and miscellaneous chemicals; petroleum refining; and plastics, synthetics, and resins). In interruption events, the substance categories most often released were mixtures, other inorganic substances, and volatile organic compounds and those most often causing injury were acids, chlorine, bases, and ammonia. Comparison events resulted in more acutely injured persons (408 versus 59) and more evacuees (11,318 versus 335) than interruption events and therefore may receive more public health attention. Because of the large number of interruption events, targeted prevention activities, including management of change procedures, lessons-learned implementation, process hazards analysis, and appropriate protection for workers could be economically advantageous and improve environmental quality. Efforts should focus on the identified areas of greater occurrence. The relationship of weather and equipment failure with interruption events needs further investigation. (c) 2006 Elsevier B. V. All rights reserved.