The aim was to compare the short- and long-term effect of a stabilization appliance with a control appliance in myofascial pain patients suffering from episodic or chronic tension-type headache. Sixty patients (mean age 29 +/- 12 years) with temporomandibular disorders (TMD) of myogenous origin and headache were studied in this prospective controlled study. Seventy-seven per cent of the patients reported episodic and 23% chronic tension-type headache at the start of the study. The 60 patients were randomly assigned to a treatment group (stabilization appliance) or to a control group (control appliance). The patients were interviewed regarding symptoms of headache and myofascial pain and clinically examined for masticatory muscle tenderness. At the 10-week and the 6- and 12-month evaluations of appliance therapy, the treatment outcome of tension-type headache was studied. At the 10-week evaluation, 17 patients dropped-out from the control group by requesting another appliance and receiving a stabilization appliance. Another patient in the control group dropped out later during the trial. In an intent-to-treat analysis, significant differences in improvement of headache between treatment and control groups were found at the follow-ups. A 30% reduction of muscles tender to palpation correlated significantly to improvement of headache at all follow-ups. The stabilization appliance seems to have a positive effect on tension-type headache, both in a short- and in a long-term perspective in patients with TMD with pain of myogenous origin.