The long-term effect of intra-articular injections of sodium hyaluronate and corticosteroid (betamethasone) was compared in a sample of 24 patients who had pain and tenderness to palpation in the temporomandibular joint (TMJ arthritis) of at least six months duration, and who had not responded to conservative treatment. The two drugs were randomly allocated to the patients. The drugs, 0.5 ml, were injected twice into the superior joint compartment of the TMJ with a two-week interval between injections. The effect on subjective symptoms, clinical signs, and bite force was assessed. At the one and two-year follow-ups both the hyaluronate-and the corticosteroid-group had significantly reduced subjective symptoms as well as clinical signs, and the maximum voluntary bite force was significantly increased. The differences in effect between treatments were not statistically significant. It was concluded that both drugs have a significant long-term effect on chronic arthritis of the TMJ and that either of the drugs can be helpful; however, sodium hyaluronate might be the best alternative due to the least risk for side effects.