Parallel to the construction of better classifications and the identification of subgroups of temporomandibular disorders, an important development has taken place in research concerning its etiology. The etiological factors implied in muscle problems refer to more generalised disorders as myofascial pain syndrome and fibromyalgia. The role of occlusal and articular factors has been brought down to realistic proportions, indicating a minor contribution. Similarly, doubt has arisen concerning the existence of a vicious cycle of pain/spasm/pain. With regard to internal derangements, emphasis has been put on the high prevalence in an otherwise normal population and the fluctuating character of the symptom. Also here, developments point towards constitutional and systemic factors, more than local influences. Trauma, however, seems to play an increasing role. The development of osteoarthrosis has been studied more in depth revealing local processes of inflammation, neurogenic inflammation and the existence of specific markers which might be important in the future. The relationship between disc derangement and the development of osteoarthrosis remains unclear.