Purpose: The purpose was to compare open and arthroscopic acrormoclavicular joint (ACJ) resection. Methods: We retrospectively reviewed 103 patients (105 shoulders) who underwent ACJ resection between 2000 and 2005. There were 56 women and 47 men with a mean age of 48 years. The mean duration of follow-up was 51 months (range, 15 to 91 months). Arthroscopic ACJ resection by use of a direct approach was performed in 81 shoulders (group A), and open ACJ resection was performed in 24 shoulders (group 13). Results were graded according to pain relief both subjectively and objectively with cross-body adduction testing and direct palpation of the ACJ, subjective shoulder value, Constant score, and improved function. Results: The Constant scores increased from 50 (range, 34 to 65) to 89 (range, 39 to 100) in group A (P < .0001) and from 46 (range, 22 to 63) to 87 (range, 43 to 100) in group B (P < .0001). There was no statistical difference in the postoperative normalized Constant score between group A and group B (P = .47), Pain with cross-body adduction testing and palpation of the ACJ improved in 76 shoulders (94%) in group A and 22 shoulders (92%) in group B. No patients had signs or symptoms of ACJ anteroposterior instability. Revision ACJ resection was performed in 5 patients (5 shoulders [6.2%]) in group A and I shoulder (4.2%) in group B (P = .37). The radiographs of the patients who underwent revision showed that 3 patients (3.7%) from group A had regrowth of the distal clavicle; in addition, 2 patients (2.5%) from group A and 1 patient (4.3%) from group B had incomplete distal clavicle excision. Conclusions: This study did not show a significant difference in the outcome between arthroscopic and open ACJ resection. Incomplete excision and regrowth of the distal clavicle are the most common causes of revision. Although only the arthroscopic group showed a small percentage of patients (3.7%) with regrowth of the distal clavicle, the number is too small to assume that this complication is the result of the arthroscopic technique only. Level of Evidence: Level IV, therapeutic case series.