PURPOSE: The purpose of this study is to compare the Phemister technique with the modified Phemister technique for the patients with Rockwood type 3, acromio-clavicular separation. MATERIALS AND METHODS: The 45 cases of 45 patients received surgical treatment for Rockwood type 3, acute acromio-clavicular separation in our hospital from Feb. 1992 to Aug. 2001 later with the follow-up study were selected as subjects. The average ages were 28.1 years old, male and female were 42, 3 persons, respectively. Physical examination and plain radiography were used for their diagnosis and the intervals between injury and surgical treatment were 7.8 days. In intraoperative finding, we performed Phemister technique in 15 cases according not to be able to repair coraco-clavicular ligament (group I), modified Phemister technique in 30 cases according to be able to repair that (group II). The average follow up period was 16.2 months, and the UCLA shoulder scoring system and the acromio-clavicular separation scoring system were used to obtain clinical results. RESULTS: Only in Group II, the complication after surgery were associated with superficial infection in two cases and K-wire migration in one case. At last follow up, there were no pain and limitation of range of motion in all cases, and two cases in Group II were found to be subluxation in radiography. Clinical results revealed excellent was 93.3%, good was 6.7% in UCLA shoulder scoring system in both groups, and excellent was 90%, good was 10% for group II in acromio-clavicular separation scoring system. CONCLUSION: The results are considered to be good with only Phemister technique in type 3, acute injury occurred in working ages.