On Jan. 17, 1995, at 5:46 a.m., an earthquake measuring 7.2 on the Richter scale shook southern area of Hyogo prefecture of Japan, including Kobe city. By this earthquake referred as the Great Hanshin Earthquake later, over 6,000 people were killed, 150,000 buildings and houses were destroyed and more than 300,000 people were temporally evacuated. Over a half of victims were reported to be elderly. We reported five survivors with senile dementia of the Alzheimer's type, who showed exacerbation or manifestation of their dementia symptoms after the quake. None of them had been injured and none of their close relatives had been killed or injured. They had been living in the downtown of Kobe for over 30 years before the disaster. Most of them had lived by themselves. Their severity of dementation were mild to moderate. They had been living without any problems and functioning fairly well. Their sons and daughters did not realize that their fathers or mothers had dementia before the earthquake. They had to move to and live with their son's or daughter's families, since their residences were destroyed by the earthquake. Shortly after that, they showed exacerbation or manifestation of their symptoms and developed delusion that their money and valuables were stolen by their daughters or daughters-in-law. We concluded that: they had been living without any problems and functioning fairly well, although they had had mild dementia symptoms; their living by themselves in communities familiar to them prevented manifestation of dementia symptoms; living together with son's or daughter's family easily promoted the development of delusion that their property was stolen by their close relatives, especially daughters or daughters-in-law in demented people.