As a group, cartilage tumours are the most common primary bone lesions. They range from benign lesions, such as enchondromas and osteochondromas, to malignant chondrosarcoma. The benign lesions result from the deregulation of the hedgehog signalling pathway, which is involved in normal bone development. These lesions can be the precursors of malignant chondrosarcomas, which are notoriously resistant to conventional chemotherapy and radiotherapy. Cytogenetic studies and mouse models are beginning to identify genes and signalling pathways that have roles in tumour progression, such as hedgehog, p53, insulin-like growth factor, cyclin-dependent kinase 4, hypoxia-inducible factor, matrix metalloproteinases, SRC and AKT, suggesting potential new therapeutic approaches.