We sequenced the coding exons of PTPN11 in 38 lesions excised from patients with Ollier disease, 2 peripheral blood samples from patients with Ollier disease, 15 lesions excised from patients with Maffucci syndrome, 4 solitary enchondromas, 9 chondrosarcomas (1 polyostotic), and 3 osteochondromas without EXT1 or EXT2 mutations. The gene discussed is EXT1; the disease is chondrosarcoma.