Chronic recurrent multifocal osteomyelitis is characterized by recurrent episodes of painful swollen lesions of the bone and overlying skin with radiographic changes and an elevated sedimentation rate. It resembles infectious osteomyelitis but with negative findings on bacterial culture and no response to antibiotics. We treated a 13-year-old girl with interferon gamma for 3 months. She had 11 episodes of chronic recurrent multifocal osteomyelitis in 2 1/2 years before therapy and has had none in the 15 months since therapy, an outcome suggesting a favorable therapeutic response.