The authors developed the Japanese-language version of the Impact of Event Scale-Revised (IES-R-J) and investigated its reliability and validity in four different groups: workers with lifetime mixed traumatic events, survivors of an arsenic poisoning case, survivors of the Hanshin-Awaji earthquake, and survivors of the Tokyo Metro sarin attack. Evidence includes retest reliability and internal consistency of the IES-R-J. Posttraumatic stress disorder (PTSD) and partial PTSD cases indicated significantly higher scores than non-PTSD cases. The IES-R-J can be a useful self-rating diagnostic instrument particularly for survivors with PTSD symptoms as a clinical concern (PTSD + partial PTSD) by using a 24/25 cutoff in total score. In analysis of scale structure, the majority of intrusion and hyperarousal items were subsumed under the same cluster, whereas avoidance items made up a separate cluster. Female patients indicated higher scores than male patients. A negative weak correlation between age and the score was found only among female earthquake survivors. The IES-R-J can be used as a validated instrument in future international comparative research.