This document provides information on Dissociative Identity Disorder (DID), formerly known as Multiple Personality Disorder. It discusses skepticism around DID and explains that dissociation exists on a spectrum from mild daydreaming to more severe identity fragmentation. The document outlines characteristics of DID like disturbances in identity, existence of distinct alters, and types of relationships between alters. Causes like childhood trauma and abuse are explored, as are popular portrayals of DID in films and books. Assessment tools, integration in therapy, and two case studies of individuals with DID are summarized.