In the first section of this encyclopedic volume, Dr. Robert Kellner surveys the biological, psychological, and psychiatric studies on nine psychosomatic syndromes, draws conclusions about the complex etiology of these syndromes, offers guidelines for diagnosis, and recommends treatments based on research findings. The second section is an overview of the various processes that lead to bodily complaints, including somatization. The author discusses how psychosomatic syndromes described in the first section contribute to the symptoms of somatoform disorders and how knowledge gained from research on treatment of psychosomatic syndromes can be applied to the treatment of somatoform disorders.