During a 37-year period, 26 patients were seen who had chondrosarcoma with additional mesenchymal components ("dedifferentiated low-grade chondrosarcoma"). Sixteen were men and 10 were women aged 30 to 85 years (median, 61 years). The tumors' chondroid areas were of borderline or low-grade malignancy. The additional mesenchymal component was histologically classified as malignant fibrous histiocytoma (16), rhabdomyosarcoma (4), low-grade fibrosarcoma (3), osteosarcoma (2), and undifferentiated sarcoma (1). Preferred locations were pelvis (10) and femur (8). Symptoms had been present for 1 year or less in most cases. Pain was the most common symptom. In 15 of 26, major amputation was the primary treatment. Twelve patients received chemotherapy, usually after developing metastatic disease, but only one achieved a partial response. Median disease-free interval after diagnosis was 4 months, median survival was 6 months, and 19 patients died within 1 year. Of 4 who survived longer than 18 months, 3 presented with a low-grade fibrosarcoma. Survival and development of metastasis appeared unrelated to cell type, initial treatment, or chemotherapy, except when the tumor's initial nonchondroid component was low-grade fibrosarcoma.