A number of nonneoplastic conditions can mimic tumors of bone. Some of the more common mimics of primary bone tumors include infectious, inflammatory, periosteal, and degenerative joint disease-associated lesions that produce tumorlike bone surface-based or intraosseous lesions. This article considers a spectrum of reactive and nonreactive processes including stress fracture, subchondral cysts, osteonecrosis, heterotopic ossification, osteomyelitis, sarcoidosis, and amyloidoma that can present in such a way that they are mistaken for a tumor arising primary in bone.