Fifteen shoulders with primary osteoarthritis and dysplastic glenoid morphology underwent shoulder arthroplasty (eleven total shoulder arthroplasties and four hemiarthroplasties). Patients were evaluated at a mean of 37 months after replacement with clinical examination, Constant score, subjective patient opinion, and radiographic examination. One glenoid component was loose, necessitating removal; the remainder of the prostheses were in place at latest follow-up. Significant improvement was observed in Constant score (32 points preoperatively vs 71 points postoperatively) and active mobility (anterior elevation, 89 o preoperatively vs 146 o postoperatively; external rotation, 7 o preoperatively vs 45 o postoperatively) after arthroplasty. This study demonstrates that the rare scenario of osteoarthritis coupled with a dysplastic glenoid can be treated successfully with shoulder arthroplasty.