The existence and characteristics of multiple personality disorder (MPD) have been debated from the time of the first case reports in the 19th century. The dispute has never been resolved, and MPD has become the most controversial syndrome known to mental health professionals. Currently, very little balanced academic material on this disorder is available, and much of the literature aims to disprove its existence as a psychiatric disorder. In the past, general understanding of MPD was guided largely by this medical literature, but in recent decades the disorder has been widely exposed to both professionals and the public through the mass media. This timely work examines MPD from an empirical viewpoint, describing the research that has been done on the disorder, as well as providing in-depth analysis of how MPD has developed over the years in relation to the media. The book identifies the earliest origins of MPD in published literature and traces the course of its development as a concept to the present. Existing data on MPD are presented in a detailed review of the current state of knowledge of the disorder including clinical description, delineation from other disorders, family history studies, follow-up studies, and laboratory documentation. The authors also point out specific areas of research that is needed before psychiatry can consider MPD an adequately validated diagnosis. This critical approach is designed to provide direction to researchers in the pursuit of a better understanding of MPD and to provide clinicians with a valuable guide.