Twenty-one patients were treated operatively for unicameral bone cysts by subtotal resection without any form of bone graft, and all but two patients had satisfactory, prompt healing. The rate of recurrence was 9%. Five patients were noted to have humeral shortening prior to any surgery, and in them the changes in the epiphyseal cartilage were noted preoperatively. Pathological fractures were thought to be the cause of the shortening in those cases.