Mental disorders are common among prison inmates. Article 26 of Japan's Mental Health and Welfare Law requires prison governors to report the impending release of inmates with mental disorders to the Prefectural governor; at the same time, documentary evidence of such inmates'psychiatric status must be submitted if they are assessed as likely to exhibit violent behavior. However, no research has been done on the implementation of this law. The goal of this study was to clarify the extent to which documentary evidence is actually included in reports issued by correctional institutions. It was found that documentary evidence is included high rates when inmates fall into 1 or more of the following 3 categories: the prison psychiatrist stated in the release report that hospitalization was necessary for psychiatric treatment; the risk of the inmate's inflicting harm on others is recognized; a violent nature and/or impulsiveness are recognized.