In an open study in 89 out-patients the effect of superoxide dismutase (Orgotein) in gonarthrosis (n = 75), post-operative or post-traumatic irritation (n = 8) and chondropathy (n = 6) was investigated. Orgotein (4 mg) was give intra-articularly once weekly for several weeks. The overall rating showed efficacy of this new antiphlogistic compound in 81 out of 89 patients (91%). In eight patients the results of treatment were insufficient. In 65 (80%) out of the 81 successfully treated patients no relapse appeared. Six patients reported reappearance of slight complaints so that in 75 out of 81 successfully treated patients, even after repeated controls, a long lasting pain relief could be achieved. Only in three cases the tolerance of Orgotein was not assessed as "very good" ("good" in one case and "moderate" in two cases). The patients reacted--despite good tolerance of the first injections--after the 4th or 5th injections with irritation and swelling as well as effusion; these symptoms were reversible within 24 hours.