Background: The purpose of this study was to evaluated results of arthroscopic treatment of the traumatic recurrent unidirectional posterior subluxation. Materials and Methods: We treated twenty-seven patients who had traumatic recurrent unidirectional posterior subluxation of the shoulder by arthroscopic labral repair and posterior capsular shift and prospectively evaluated for a mean of thirty-nine months (range,24 to 85 months). Patients who had posteroinferior instability, multidirectional instability, atraumatic onset, or revision cases were excluded. There were twenty-five male and two female patients with the mean age of twenty-one years (range, 14 to 33 years). All patients were involved in sports activity. All had a significant traumatic event prior to the onset of the instability. Stability, motion, three objective measurement (UCLA, ASES, and Rowe scores) and two subjective measurements (pain and function visual analogue scale) were evaluated. Results: The most common finding in magnetic resonance image-arthrogram was separation of the posteroinferior labrum without displacement in 9 patients, In arthroscopic examination, all patients had one or more lesions in the posterior inferior labrum and capsule. The most common finding was incomplete stripping of the posterior inferior labrum (18 patients). The posteroinferior capsule subjectively appeared to be stretched in twenty-two patients. At follow-up, all patients had improved shoulder function and scores(p