Glenohumeral instability remains a very complex and sometimes challenging diagnostic problem. In most patients, the diagnosis relies mainly on history and physical examination. Radiologic studies provide further information about associated lesions. Although the initial imaging modality for any shoulder condition should be routine radiographs, additional imaging modalities are utilized to evaluate treatment options and prognosis. Computed tomography arthrography and magnetic resonance imaging provide valuable information. However, magnetic resonance arthrography may be required in cases in which it is uniquely appropriate for its multiplanar capability and excellent soft tissue contrast.