The clinical trials performed with bovine superoxide dismutase (SOD) are reviewed. SOD, applied intraarticularly at a dosage of 2-16 mg, proved to be effective in osteoarthritis of the knee joint in three placebo-controlled and one steroid-controlled double-blind trials. Its efficacy in other inflammatory joint disorders is documented by uncontrolled trials. Similarly, some controlled and many open studies support the efficacy of locally injected SOD in periarticular inflammation. Systemic treatment of rheumatoid arthritis by SOD at the dosages indicated yielded disappointing results. Well documented, though open uncontrolled studies demonstrated beneficial effects of locally administered SOD in radiation cystitis, interstitial cystitis and Peyronie's disease. Tolerance is good, but allergic reactions at low incidence have to be anticipated. Human SOD derived from recombinant microorganisms is being developed to explore its therapeutic potential particularly in ischemia-reperfusion damage, adult respiratory distress or similar conditions.