This publication examines the following topics in more detail than others: the subject of forensic psychiatry, the organization, procedure for appointing and conducting a forensic psychiatric examination, the subject of a forensic psychiatric examination in criminal and civil cases, penitentiary psychiatry. The legal basis for the activities of a forensic psychiatric expert is outlined in detail. Regulatory legal acts are given as of October 1997. The forms of mental illness are presented in accordance with traditional views on them in domestic psychiatry and taking into account the international classification of diseases, 10th revision (ICD-10), the introduction of which is planned in the near future. Volume of the textbook and The way the material is presented makes it possible to use it not only in the preparation of undergraduates, graduate students, and participants in postgraduate education courses, but also in the practical work of investigators, prosecutors, judges, lawyers, and forensic psychiatric experts.