This document provides an overview of Harry Stack Sullivan's interpersonal theory of psychiatry and interpersonal psychotherapy. It discusses Sullivan's biography, major works, and theoretical contributions. Key aspects of Sullivan's personality theory are outlined, including his emphasis on interpersonal relationships, needs, anxiety, security operations, and the development of the self-system. Sullivan's developmental theories, including his stages of cognitive and social development, are presented. His view of psychopathology as problems in living resulting from excessive anxiety is explained. Finally, the four steps of Sullivan's interpersonal psychotherapy - inception, reconnaissance, detailed inquiry, and termination - are described.