Arthroscopic treatment of shoulder instability involves two techniques mainly, transglenoid suture technique and anterior anchoring system. However, anterior anchoring system has some disadvantages such as limited indication, high cost, technical difficulty and incapability to suture or reconstruct for all types of Bankart lesion. Disadvantages of transglenoid suture techniques are indirect suture tie, bump effect and possibility of the suprascapular nerve injury. The authors use modified transglenoid suture technique (Rhees method) for shoulder instability involving Bankart lesion, type II SLAP lesion and capsular laxity. The purpose of this study is to accurately describe the relationship between the major neurovascular structures and the pinning sites used in transglenoid suture technique (Rhees method). Placement of two or three arthroscopic Beath pinning sites was simulated in four fresh cadaveric shoulder specimens by placing Steinman pins into the glenoid rim under open field. The specimens were then dissected and the relationship of the pinning sites to the suprascapular nerve and suprascapular artery were recorded. In Bankart lesion repair, safe zone of pinning sites were 2 and 5 oclock in two portals in right shoulder, safe zone of pinning sites were 7 and 10 oclock in two portals in left shoulder. Safe direction of pinning was as possible as inferomedial side in scapula. In type II SLAP repair, safe zone of pinning sites were 2 oclock and just above 2 oclock of glenoid in right shoulder and 10 oclock and just above 10 oclock of glenoid in left shoulder. Safe direction of pinning was pararell to glenoid cavity and slightly superior in horizontal plane. From this study, these sites and directions appeared to be safe. Proper pinning depends on careful attention to the topographical anatomy about the shoulder.