PURPOSE: The purpose of this study was to present a personal view of the development of prevailing opinions about temporomandibular disorders (TMD) during the last half century from a mechanistic to a psychosomatic concept. It also presents some hypotheses concerning: (1) the role of stress in the etiology of human oral parafunctions and its relationship to oral stereotypies in domestic animals; and (2) the pathogenetic mechanisms of masticatory muscle pain. MATERIALS AND METHODS: The basis for this article was a review of personal experiences derived from clinical and research work with TMD patients. Studies of both older and more recent literature on TMD and related disorders - especially in the fields of stress research, psychosocial medicine, occupational medicine, and etiology - were also used. RESULTS: A clear line is found in the development of the ideas on etiology, pathogenesis, and therapy of TMD, from the mechanistic attitude of Costen syndrome through the introduction of psychologic and psychophysical theories by the Columbia and Chicago schools to the now increasingly accepted biopsychosocial concept and the view of refractory TMD as a chronic pain condition. CONCLUSION: The formerly dominant bite-centered therapies - including intraoral appliances, the effects of which still are unexplained - appear to be increasingly banished to the domain of placebo Hence, to an ever-increasing extent occlusal treatments are replaced by physiotherapy and cognitive behavior therapy. The presented hypotheses may have implications for the understanding of the origin of oral parafunction and masticatory muscle pain.