The purpose of this study was to determine the correlation between routine radiography and magnetic resonance (MR) imaging in the analysis of the acromioclavicular (AC) joint osteoarthritis (OA). MR imaging studies of the shoulder in 50 patients performed over a 1-year period at a single institution with corresponding conventional radiographic examinations performed within 1 month of the MR imaging study were restrospectively evaluated by the consensus of two musculoskeletal radiologists with special attention to the AC joint. As conclusion, information provided by conventional radiography in the analysis of AC joint OA does not correlate with that provided by MR imaging. AC joint OA is more frequently detected with MR imaging than with radiography. MR imaging provides better assessment of the full extent of AC joint OA and its effect on the underlying RC.