Twenty-five temporomandibular joints (TMJs) in 15 patients with chronic arthritic disease were treated with synovectomy and diskectomy. Twenty patients with internal derangement of 27 TMJs treated with diskectomy served as a control group. A response in pain relief was seen in 73% of the patients with chronic arthritic disease and in 80% of the patients with internal derangement 3 yr postoperatively. In both groups of patients a significant increase in mouth opening capacity and lateral movement of the mandible was seen postoperatively, with no significant difference in the improvement between the two groups. Four patients with chronic arthritic disease were reoperated within the 3-yr observation period. This study indicates that synovectomy and diskectomy of the TMJ may reduce pain and improve mandibular function in patients with severe chronic arthritic TMJ disease.