The aim of this thesis was to evaluate the indications for and the results of temporomandibular joint (TMJ) surgery in patients with long-standing severe orofacial pain and dysfunction as well as in patients with fractures of the condylar neck. The patients with long-standing pain and dysfunction had had symptoms for a mean time of 4 years, had been treated conservatively for a mean time of 2.5 years, and had undergone numerous conservative treatment methods without improvement except for a minor increase in mouth opening capacity. The indications for surgery were strict; only 1% or less of all the patients referred to the departments with a diagnosis of temporomandibular disorder (TMD) were prescribed surgery, which was considered to be the only remaining option. The TMJ surgery reduced pain, sleeping problems, and analgesic consumption and improved mouth opening capacity. The procedure showed low morbidity except for a facial nerve disturbance in three patients. Postoperatively, the bite force was observed to be normalised, and the radiographic examination showed moderate to severe osteoarthrotic changes. These changes, though extensive, were considered to be the normal outcome of diskectomy and without clinical significance, even though they resembled degenerative joint disease. In study V, surgery was performed on patients with a clear diagnosis of anterior disk displacement (ADD) with or without reduction. The preoperative pain and mouth opening capacity were markedly improved as well as other subjective symptoms. Although surgical morbidity was low, some radiographic changes were clearly detectable. In agreement with earlier reports, patients with a distinct diagnosis of ADD with or without reduction were clearly helped by diskectomy. In cases of ADD with or without reduction, it can be concluded that unsuccessful conservative treatment should not exceed 3-6 months but be discontinued in favour of the documented advantages of surgery in these cases. Patients with ankylosis should be treated surgically without delay. Unclear diagnoses such as arthralgia and osteoarthrosis with symptoms should be excluded from surgery unless overlapping muscular hyperactivity has been excluded as a major cause of the patients problem. Diskectomy is a useful surgical procedure for patients with severe long-standing TMD. It was shown in study VI that patients with dislocated fractures of the condylar neck can be successfully treated with open surgical reduction when the dislocation is large and associated with symptoms and limited function. When cognitive-behavioural profiles were measured psychometrically in study VII, a dysfunctional profile was more common in patients with myofascial pain and pain with an obscure origin than in other patients diagnosed with TMD. The dysfunctional profile was also common in patients in whom treatment of a conservative or surgical nature had failed. Among TMD patients with disk displacement, adaptive copers were most common in successfully diskectomized patients and least common in patients about to undergo invasive treatment.