The anti-arthritic activity of the superoxide scavenging compound CTC 23 was tested in murine type II collagen-induced arthritis (CIA). CTC 23 demonstrated a dose-dependent prevention of the onset of CIA, with a significant reduction of disease incidence in mice receiving prophylactic administration of CTC 23 from 2.5-5 mg/kg/day. CTC 23 also delayed the development of the anti-collagen immune response, causing a significant decrease in antibody levels 14 days after immunization. CTC 23 reduced the arthritis score and number of involved limbs in mice with established CIA. The results suggest that CTC 23 acts as a disease modifying anti-arthritic compound to prevent the progression of the experimental arthritis.