Anterior glenohumeral instability is mainly due to the Bankart lesion and capsular stretch. The differentiation between the Bankart lesion and capsular laxity may not be readily apparent on clinical examination. So, increasing attention has been directed toward preoperative evaluation of the labral lesion and capsular laxity. MRI and MR Arthrogram of 55 shoulders, 40 stable shoulders and 15 unstable shoulders that were confirmed by arthroscopic surgery, were reviewed to evaluate the labral and capsular shapes, especially the lesions of labroligamentous complex. To evaluate and compare the capsular laxity, we measured the anterior capsular insertion type, capsular ballooning, capsular insertion angle and anterior band of inferior glenohumeral ligament. And the following results were obtained; 1) The shape of anterior labrum was varied in the superior, middle and inferior potions in 40 stable shoulders. The anterior labral lesions were shown as torn(eight cases), displaced(six cases) and no detectable labrum(one case), in 15 unstable shoulders. Also, there were a significant di fference in the evaluation of the anteior labrum shape between MRI and MR arthrography. 2) There were not a significant difference in the type III capsular insertion type, capsular ballooning and capsular insertion angle between the stable and unstable shoulders. However, it was found that the shape of the anterior band of the inferior glenohumeral ligament had definite difference between the two groups. And so, more experience and attention should be given for the accurate preoperative evaluation of the anterior labroligamentous complex in shoulder instability.