Temporomandibular disorders remain a common cause of visits to primary care physicians, internists, pediatricians, and emergency departments. Advances in the clinical diagnosis, radiographic imaging, and classification of these disorders have improved long-term management. There are several types of disorders of the masticatory muscles and the temporomandibular joint as well as associated structures and each may have a complex cause, clinical course, and response to therapy. Host susceptibility plays a role at several stages of these disorders. Future research offers greater possibility in defining this heterogeneous group of disorders and providing more focused and effective treatment strategies.