SARCOMATOUS TRANSFORMATION OF the enchondromas is a well-known complication of Ollier's disease, and nonsarcomatous malignancies have usually been associated with Maffucci's syndrome. Only 13 cases of multiple enchondromatosis associated with intracranial gliomas have been described, 5 of which were in patients with Ollier's disease. We describe three patients, including identical twins, who had both Ollier's disease and primary brain tumors. This is the first report of Ollier's disease in identical twins. These three cases support the theory that Ollier's disease and Maffucci's syndrome may represent a spectrum of the same disease process rather than two distinct diseases.