Erosive osteoarthritis is a disorder that most often involves the hands of postmenopausal women. It can begin abruptly with pain, swelling, and tenderness. Distal interphalangeal joints are involved most frequently, followed by proximal interphalangeal joints. Occasionally there is metacarpophalangeal, carpal, or large joint involvement. The female-to-male ratio is approximately 12:1. There are no known HLA associations. Laboratory studies generally are negative. A mild elevation of the sedimentation rate may occur. Radiologically, the disorder is characterized by central erosions and the "gull wing" deformity. Synovial pathology has shown changes consistent with both rheumatoid arthritis and osteoarthritis and manifests the stage of disease at the time of biopsy. The etiology remains obscure, but hormonal influences, metabolic disorders, and autoimmunity have been implicated. Treatment is largely supportive with physical therapy, nonsteroidal antiinflammatory drugs, and occasionally prednisone. Overall prognosis is good, although deformity and impairment of hand function may occur. For this reason, a reassessment of treatment strategies may be in order.