This chapter describes the data sources that are available for verifying the ages of the oldest-old in Japan. These sources can be both official and non-official documents. The official documents consist primarily of education and employment records issued by administration offices. The non-official documents include the testimonies of the centenarians themselves, their relatives, and their care workers; as well as media reports. We collected information from these official and non-official sources in order to confirm that three Japanese individuals who had reportedly survived to age 115 were indeed that old. The first of these individuals is Mr. Jiroemon Kimura (J.K.), who spent most of his life in his birth place. In his case, we were able to gather information from various sources, including from official and non-official documents. But for the other two individuals, Mrs. Misao Okawa (M.O.) and Mrs. Chiyo Miyako (C.M.), who relocated several times within urban areas, we were able to collect only a limited amount of information. In particular, we were unable to find many official documents about their original family members. These three cases suggest that the availability of the data needed to verify the ages of individuals who were born around 1900 might differ depending on the following three conditions: whether the person has moved from his/her place of birth, whether the person has been living in rural or urban areas, and whether the person is male or female.