Sarcomas originate from bone or soft tissue. The most common bone sarcomas are osteosarcomas, Ewing sarcomas, and chondrosarcomas. Soft tissue sarcomas develop in fibrous tissue, fat, muscle, blood vessels, and nerves. Historically, soft tissue sarcomas of the trunk and extremities were reported separately from those of visceral organs (e.g., gastrointestinal and gynecologic sarcomas). This chapter discusses the classification, epidemiology, diagnosis, staging, and treatment of sarcomas of bone and cartilage, and classic soft tissue sarcomas. Management of Kaposi sarcoma, gastrointestinal stromal tumors (GISTs), mesothelioma, and rhabdomyosarcoma is also described. Figures include images of patients with osteosarcoma, liposarcoma, uterine leiomyosarcoma, GIST, and osteosarcoma in a patient with Paget disease of bone. Tables list epidemiologic features of sarcomas, a summary of sarcomas by histology, familial syndromes associated with increased risk of sarcoma, survival rates in sarcoma patients, staging of soft tissue sarcomas, and results of a meta-analysis of doxorubicin-based adjuvant chemotherapy for localized resectable soft tissue sarcoma. This chapter contains 126 references.