Primary fibromyalgia syndrome (PFS) is a form of nonarticular rheumatism characterized by muscular pain and stiffness, commonly located in the neck-, shoulder-, back-, and pelvic regions. The most common finding in patients with mandibular dysfunction (MD) is pain or tenderness of the masticatory muscles, but tender and painful neck and shoulder muscles are also often found in relation to jaw muscle affection. Complaints presented by patients suffering from musculoskeletal conditions may overlap one another. Indeed, there may be some common causative factors for these complaints. To test the hypothesis that some complaints by PFS patients could be explained by mandibular dysfunction, we have investigated the subjective symptoms and the clinical state of the stomatognathic system in eight patients suffering from PFS. According to the Helkimo anamnestic dysfunction index, six patients were classified as having severe signs of MD. The Helkimo clinical dysfunction index revealed severe or moderate dysfunction in all patients. Recurrent headaches was reported by half of the patients. In conclusion, the present study shows that PFS patients also may suffer from mandibular dysfunction. Thus, an examination of the function of the stomatognathic system would be an important part in the investigation to elucidate possible etiological factors behind the reported complaints by PFS patients. PFS may also be of etiological importance for mandibular dysfunction.