A tomographic investigation was performed on 51 randomly-selected rheumatic patients, according to American Rheumatism Association criteria. Fourteen males and 37 females, aged 26 to 73 (mean age 50.9) were examined in order to identify the prevalence of temporo-mandibular joint involvement. By means of a special examination form, a contemporary clinical survey of both signs and symptoms of mandibular dysfunction was also conducted: the data were used for calculating the Helkimo anamnestic and clinical dysfunction indices. As for X-ray diagnosis, and original linear and angular analysis was proposed to measure the relationship between condyle and fossa in intercuspal position and during opening: the anterior joint space often increased and protrusive condylar path was reduced in more than 41% of patients. Structural changes were also evaluated by classifying the shape of both the condyle and the glenoid fossa (rounded, wedge-shaped and flattened). A special score was used to quantify these morphological features: only 4% of the whole of joints resulted uninjured. The most involved joint portions were the articular tubercle and the anterior condylar pole. Many cases were demonstrated of marked resorption and remodelling of the condyle, of increased joint space and erosion of the fossa; in other instances, reduced joint spaces and sclerosis were observed, depending on associated degenerative arthritis (usually more painful). Sex and age differences were not significant. Severity of clinical dysfunction and seriousness of the lesions coincided, whereas subjective symptoms were relatively independent. At any rate, the survey demonstrated a clear prevalence of structural, as well as functional, involvement of the temporo-mandibular joint in rheumatoid arthritis and suggested a more careful and multimodal therapeutic approach.