Oral function was evaluated in a group of 13 patients with muscle contraction headache (MCH), 7 patients with common migraine (CM) and 18 patients with 'combination headache' (CM + MCH) and in a control group of 25 normal persons who had never had a headache. Malocclusion and loss of molars were rare in both groups. Impaired denture function and joint disturbances were more frequent in the headache patients but not significantly so. Clenching and grinding teeth and tongue pressure were all significantly more common in headache patients. Tenderness of pericranial muscles was present in all headache patients with severity increasing in the order CM, MCH, CM + MCH; it was absent in all the controls. On the average 9 tender spots were found per patient. Pressure on tender spots evoked pain in other areas (referred pain) in 29 of 38 headache patients. The abnormal tonic hyperactivity in the masticatory muscles and the neck may be the cause of tenderness which again may be an important source of pain in these patients.