Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by the presence of multiple exostoses. Three genetic loci have been identified, of which two (EXT1 and EXT2) have tumor suppressor activity. HME greatly increases the risk to develop sarcoma in the dysplastic tissue. The authors report an 8-year-old girl with HME who developed acute myeloblastic leukemia.