A tomographic investigation was performed on 51 randomly selected patients with Rheumatoid Arthritis in order to identify the prevalence of the temporo-mandibular joint involvement and the relationship with the clinical dysfunction and occlusal state. The relation between the condyle and the fossa in intercuspal position and during opening were measured: protrusive condylar path often got reduced. Articular shape and structural changes were also evaluated: only 4% of total joints resulted uninjured. The survey showed a significant incidence of structural as well as functional involvement of the tmj. Instead subjective symptoms and dental support seemed to be relatively independent, to confirm the heterogeneity of factors in masticatory dysfunction.