A psychosomatic syndrome is defined as a syndrome in which psychological processes play a substantial role in the etiology of the illness in some of the patients. The main conclusions on the extent of the biological and psychosocial contributions to several psychosomatic syndromes are presented and the relationship of these syndromes to somatization and somatoform disorders is discussed. The syndromes summarized include fibromyalgia, chronic fatigue, motility disorders of the esophagus, nonulcer dyspepsia, irritable bowel syndrome, urethral syndrome, behaviors causing disturbances of physiology, and some defined pain syndromes. The findings suggest that the extent of the biological and psychosocial contributions vary among these syndromes as well as among individuals with the same syndrome. In some syndromes the extent and nature of the biological contribution has not been established with certainty. There is evidence to suggest that many of the phenomena of the somatoform disorders are caused by clustering of psychosomatic syndromes or their incomplete or atypical manifestations and a low sensation threshold. The results of the controlled studies of various methods of psychotherapy and drug treatments of the psychosomatic syndromes are listed; these studies have practical implications because the adoption of these methods is likely to enhance the efficacy of the treatment of somatoform disorders.