One hundred individuals with ankylosing spondylitis (AS) and a comparison group comprising 57 individuals without joint symptoms or disease were studied for correlations between subjective, clinical, and radiographic features in the stomatognathic system and the short-term effect of occlusal splint therapy. There was a correlation between radiographic findings in the temporomandibular joint (TMJ) and subjective and clinical symptoms from the stomatognathic system in individuals with AS but not in the comparison group. There were also more and stronger correlations between clinical signs of TMJ involvement and subjective and other clinical symptoms from the stomatognathic system in the individuals with AS than in the comparison group. There are thus strong indications that the subjective symptoms, the clinical signs, and the radiographic findings in the TMJ of the individuals with AS were caused mainly by this joint disease. The short-term effect of treatment with occlusal splints was investigated in seven of the individuals with AS, who had clinical dysfunction index II or more in accordance with Helkimo. No statistically significant improvement of the subjective or clinical symptoms from the stomatognathic system was found, although a reduction of clinical symptoms was noted in five of the seven individuals.