Objectives: To compare the short- and long-term effectiveness of a prefabricated occlusal appliance with a stabilization appliance for the treatment of headache in myofascial pain patients. Methods: Sixty-five myofascial pain patients of whom 57 reported headache were included in a randomized controlled trial at two centres for Stomatognathic Physiology in Sweden and Finland. Patients were randomly assigned to a prefabricated appliance (R-group, 27 women, 5 men, mean age 38 years) or a stabilization appliance group (S-group, 31 women 2 men, mean age 37 years). RDC/TMD was used for history-taking and clinical examination. Frequency and intensity of headache were assessed using a verbal scale (1=continuous, 2=recurrent, 3=rarely) and a numeric rating scale (NRS) respectively at baseline, 10-week, 6-and 12-month follow-ups. Results: At baseline there were no differences between the groups regarding frequency and intensity of headache. At the follow-ups a statistically significant decrease in both frequency and intensity was observed within the two groups without any differences between the groups. At baseline 72% and 70% in the R and S groups reported recurrent or continuous headache which decreased significantly (p< .01) within both groups to 44% and 31% at 10-week and to 26% and 18% at the 12-month follow-up. Mean intensity (NRS) of headache at baseline decreased within both groups from 6 to 3 at 10-week follow-up and to 2 and 3 in the R and S groups respectively (p< .001) at 12-month follow-up. Conclusions: In both short- and long-term the prefabricated appliance seemed to have a similar effectiveness in the treatment of headache in myofascial pain patients.