The monograph contains material reflecting modern ideas about borderline mental disorders and current views on the biopsychosocial approach to their understanding and diagnosis. The main clinical forms of diseases included in the group of borderline mental disorders are considered, the criteria for making a multidimensional diagnosis, including clinical, psychological, social and functional aspects, allowing to fully assess the patient's condition, resources, social functioning, dynamics and prognosis of the disease, are proposed and substantiated. The monograph is intended for psychiatrists, psychotherapists and medical psychologists, and can also be recommended as a guide for students of the postgraduate education system.