Aims: To compare the short-term effectiveness of a stabilization appliance with a prefabricated occlusal appliance in myofascial pain patients in a randomized controlled trial. Methods: Sixty-five patients at 2 centres were assigned to a stabilization appliance group (S group, n = 33) or a prefabricated appliance (Relax) group (R group, n = 32). The patients had been suffering from temporomandibular disorder (TMD) pain for 3 months to 40 years. The patients were examined for symptoms and signs of temporomandibular disorders according to the Research Diagnostic Criteria for TMD and treated by a general practitioner. Treatment outcomes regarding pain, registered on a visual analogue scale, and overall ratings of pain, registered on a verbal scale, were evaluated at 6- and 10- week follow-up appointments, and the data from the groups were compared statistically, results: The main treatment outcome in the 2 groups was a positive improvement of overall symptoms without any statistically significant differences between groups at either 6 or 10 weeks. At the 6-week follow-up, 72% of ala patients reported a 30% reduction of the worst pain, and 55% of the patients reported a 50% reduction of the worst pain, whereas at the 10-week follow-up, the percentages were 69% and 61%, respectively. According to the verbal scale, 85% of all patients reported themselves to be “better,” “much better,” or “symptom-free” at the 6-week follow-up, and 83% reported this at the 10-week follow-up. Conclusion: The effectiveness of the prefabricated occlusal appliance seemed to be the same as that of the stabilization appliance. The prefabricated appliance can therefore be recommended as a short-term therapy in adult patients with myofascial pain.