Background: Dedifferentiated chondrosarcoma (DDC) accounts for a small proportion of chondrosarcomas. They demonstrate aggressive behaviour with a high rate of local recurrence and systemic progression resulting in poor long-term survival rates. Due to its relatively low incidence, previous studies have grouped different histiotypes together to achieve adequate study numbers for analysis. Methods: This retrospective study examines the clinical course and the role of chemotherapy in the subgroup of patients with DDC where osteosarcoma is the predominant dedifferentiated component. Between 2000-2010, 21 patients were identified. Results: The mean age at presentation was 64 years (range 35-80 years). 12 patients were considered unfit for chemotherapy, whilst 2 patients declined chemotherapy. 5 patients received neoadjuvant chemotherapy, with less than 90% necrosis demonstrated in all these cases. 3 patients received post-operative chemotherapy. The median survival for the entire group was 9.5 months. In the 7 patients who received chemotherapy, the median survival was 17 months, and those who had chemotherapy had a greater median time to local recurrence. Conclusion: This study demonstrates that cytotoxic chemotherapy may be offered to appropriately selected patients.