Background: Regarding the high prevalence of degenerative disease of the Acromioclavicular joint and invention of new sensitive diagnostic methods on one hand, and several reports approving the influence of arthroscopic Mumford method in affected patients (which we lack the evidence in this regard in our country) on the other hand, we conducted this research on patients referred to Taleqani hospital between 2004-2007. Materials and Methods: This research was carried out by clinical trial comparing pre & post- operative patients accepting this methods due to failure of previous conservative threatments. All patients were operated by Arthroscopic Mumford procedure and range of motion (ROM), strengh and pain were determined in pre-operative and post-operative stages by standard methods. They were followed up for at least three months and the efficacy of this method was measured on the basis of above indices and any changes were judged clinically by statstical tests such as paired t-test and McNemar's test. Results: 41 patients were enrolled (87% male, 13% female) whose mean age were 48 years old. Before treatment, 26.8% oof elderly patients had moderate pain and 73.2% had severe pain, whereas, after treatment 78% of them had experienced no pain and 22% had mild pain (P<0.000). Indices of ROM improved by at least 33%, with the maximum of 60% (P<0.05). Power strenghts of flexion and abduction got better but internal and external rotation remained the same. Conclusion: Arthroscopic Mumford procedure seems to be effective for mentioned cases and can be recommended for them, accordingly.