Background Extraosseous osteosarcoma is rare, and the most appropriate therapy is unclear because there are few studies regarding its treatment. The effectiveness of radiation and chemotherapy remains uncertain owing to conflicting results in previous reports. Questions/purposes To review our experience with contemporary multimodality treatment, we asked: (1) What is the disease-specific survival and local relapse-free survival? (2) Does American Joint Commission on Cancer (AJCC) stage, tumor size, or location relate to disease outcome? (3) Does radiation therapy improve local control or survival? (4) Do doxorubicin and ifosfamide improve local control or survival? Methods Between 1990 and 2012, we treated 40 patients for localized, high-grade extraosseous osteosarcoma. In this retrospective study, we could determine the status of 36 patients (90%) either to death or for a minimum of 24 months of followup; four (10%) were lost to followup before 24 months. There were 11 patients with AJCC Stage IIA and 25 with Stage III disease. All patients underwent wide surgical excision. Of the patients with Stage IIA disease, four received radiation and none received chemotherapy. Of the patients with Stage III disease, six received radiation, seven were treated with chemotherapy, and six received radiation and chemotherapy. During the study period, high-dose doxorubicin and ifosfamide was the preferred chemotherapy regimen for patients younger than 60 years with normal cardiac and renal function. Local relapse-free survival and disease-specific survival were determined by Kaplan-Meier analysis using a prospectively maintained institutional database supplemented by information from the institutional tumor registry. The Cox proportional hazard model was used to determine the effect of various factors on local recurrence and patient survival.One of the authors certifies that he (SP), or a member of his or her immediate family, has or may receive payments or benefits, during the study period, an amount of less than USD 10,000 from CytRx (Los Angeles, CA, USA), an amount of less than 10,000 USD from Janssen Pharmaceuticals/Johnson & Johnson (Titusville, NJ, USA), and an amount of USD 10,000-USD 100,000 from Novartis (Basel, Switzerland). All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research 1 editors and board members are on file with the publication and can be viewed on request. Clinical Orthopaedics and Related Research 1 neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use. Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. Results At 5 years, local relapse-free survival was 47% (95% CI, 27%-64%), and disease-spe...