In 7 patients given a standard treatment during spontaneous attacks of common migraine, activity in the temporal and sternocleidomastoid muscles was studied for 140 min. Pain and nausea ratings were taken with 20 min intervals. Baseline recordings were obtained from all patients during a period without headache and from 8 dental students without a history of migraine. During the attack of migraine, activity in the anterior temporal muscles significantly exceeded the patient's own baseline recordings and all muscles were activated more strongly than in the control sample. The increase in per cent of maximal muscle activity was insufficient to account for ischemic pain. Following treatment the activity of the temporal and sternocleidomastoid muscles decreased in 5 patients at the same time as the pain and nausea to the level of the controls. It is suggested that the moderate increase of activity on admission was a residual from stronger contractions earlier in the attack. In addition to cessation of the attack, placement in supine position and intake of diazepam may have contributed to the decline of muscle activity.