Aim: To compare the long-term effect of treatment with a stabilization appliance (group T) and treatment with a control appliance (group C) in temporomandibular disorder (TMD) patents with myofascial pain. Methods: In this controlled trial, 60 patients (mean age 29 years) with myofascial pain were evaluated after 10 weeks of treatment with either a stabilization appliance or a control appliance. All 60 patients were then assigned to 1 of 3 groups according to demand for treatment. Seventeen patients from group C requested another appliance and were given a stabilization appliance, thus creating a mixed group (group M). Results: A significant difference was found between groups T and C. at the 6- and 12-months follow-ups, a significant reduction in myofascial pain, as measured on a visual analogue scale, was found in all three groups. A significant decrease in frequency and intensity of myofascial pain was found in group T at the follow-ups. A significant decrease in number of tender sites on the masticatory muscles was found in group T at the follow-ups. Conclusion: The results support the conclusion that the positive treatment outcome obtained by use of a stabilization appliance to alleviate the signs and symptoms in patients with myofascial pain persisted after 6 and 12 months. Most patients in groups T and M reported positive changes in overall subjective symptoms in this trial. We therefore recommend user of the stabilization appliance in the treatment of TMD patients with myofascial pain.