OBJECTIVES: A nerve agent sarin (isopropyl methyl phosphonofluoridate) was released in Matsumoto city, Japan, on 27 June 1994. About 600 people were affected by the sarin, including seven who died. Fifty two rescuers engaged in helping the victims and 18 were affected. The aim was to investigate how the rescuers were affected by sarin. METHODS: Health examinations and a questionnaire survey were conducted with all rescuers. RESULTS: A rescuer who was one of the first engaged and who worked for about five hours in areas contaminated with sarin was admitted to hospital after poisoning; the others did not consult doctors although they showed slight muscarinic symptoms. The later the rescuers started their work, the less likely they were to experience symptoms of sarin exposure, and no one starting work 270 minutes after the original release of sarin was affected. The symptoms of exposure included ocular pain, darkness of visual field, nausea, vomiting, headache, rhinorrhea, narrowing of visual field, sore throat, fatigue, and dyspnoea, which were similar to those reported by the citizens who were sarin victims. There were no rescuers who had abnormal physical or neurological signs associated with sarin at the time of the physical examination conducted three weeks after the sarin release. A year after the sarin incident, the symptoms of all the rescuers had resolved. CONCLUSIONS: Rescuers should protect themselves with appropriate clothing, gloves, and a mask to prevent a secondary disaster for at least 24 hours after a similar accident.