Ollier's disease is a rate affliction (not more than approximately 100 cases have been reported over a 30-year period) characterized by bone dysplasia in which evolution to degenerative neoplasia has been described. Diagnosis of chondrosarcoma is delicate in these cases. It is a kind of slowly evolving low grade malignant tumor. Surgery is the primary treatment course, and can lead to remission. Prognosis, depending on the number and dimension of the lesions, their localization and metastasis prevention, is usually good, but relapses are relatively frequent: 25 to 50%. In case of relapse, radiotherapy and chemotherapy were tested but their efficacy is limited. We report here two clinical cases and discuss literature data.