This report describes the rescue activities and the exposure of rescue and hospital personnel from the first unexpected nerve gas terrorist attack using sarin (isopropyl methylphophonofluoridate) in the city of Matsumoto at midnight on June 27, 1994. The details of the emergency activities in the disaster were studied based on the records from emergency departments of the affiliated hospitals and records from the firehouse. About 600 people, including residents and rescue staff, were exposed to sarin gas. Fifty-eight residents were admitted to hospitals, and 7 died. Among 95 rescuers and the duty doctor from the doctor car, 8 had mild symptoms of poisoning. All the rescue activity took place without gas masks or decontamination procedures. In this case of unexpected mass exposure to sarin gas, the emergency rescue system for a large disaster in Matsumoto city, which had been established for a conflagration or a local earthquake, was effective.