To analyze the improvement of shouder function after arthroscpic subacrominal decompression and open repair for complete rotator cuff tear, we performed a prospective study in 14 patients using self evaluation form from the American Shouder and Elbow Society(ASES). All patients were treated with arthrscopic biplanar subacromial decompression and open repair by use of bony trough and followed for more than 1 year from November 1994 to June 1996 in Dankook university hospital. All patients were assessed preoperatively and at final follow-up using the standardised method of research committee of American shoulder & elbow surgeons. Tears of the rotator cuff were divided into medium(8 shoulders), large(3 shoulders) and massive(3 shoulders). Most of the patients were heavy laborers. Average age was 56.2 years (51-73 years). There were 9 male and 5 female patients. The dominant arm was affected in 8 shoulders. Postoperative abduction brace was used in all cases and passive range of mortion exercise was started from postoperative third day. At average follow-up of 17 months, average pain scores decreased to 0.8±1.1 from 6.9±2.3. Scores of ASES evaluation form increased to 87.3±12.2 from 35.8±16.3(p<0.05). As to the range of mortion, only internal rotation improved from T12 to T8(p<0.05). Thirteen patients achieved excellent or good result. Twelve patients returned to initial occupations. Arthroscopy is helpful to define the tear size which may affect the surgical approach and open repair by use of bony trough and tunnel is useful to recovery of shoulder function.