Objective: The authors sought to identify prognostic factors in the management of extremity soft tissue sarcoma. Summary Background Data: The surgical management of soft tissue sarcoma has evolved because of advances in therapy, resulting in increased limb preservation and quality of life. However, identifying a subset of patients most likely to benefit from adjuvant chemotherapy has been difficult to achieve. Methods: A retrospective analysis of a prospective data base of 182 patients with extremity sarcomas from 1970 to 1992 was performed. Results: A histologic diagnosis of Ewing's sarcoma, synovial sarcoma, and angiosarcoma was associated with a 13-fold increased risk of death compared with liposarcoma, fibrosarcoma, and malignant peripheral nerve sheath histologic types after having adjusted for the other prognostic factors (p < 0.001). In addition to histologic type, high-grade sarcomas (p = 0.018), sarcomas greater than 10 cm in size (p = 0.006), and age at diagnosis (p = 0.016) were found to be important prognostic factors for survival but not for local recurrence. For the first time to their knowledge, the authors showed that mean mitotic activity has prognostic value after having adjusted for other prognostic factors, such as grade (p = 0.005). The only prognostic factors predictive for local recurrence were whether the patient presented with locally recurrent disease (p = 0.0001) or had microscopically positive margins (p = 0.052). Conclusions: The use of mitotic activity along with grade, size, histologic type, and age at diagnosis is prognostic for survival in extremity soft tissue sarcoma. The use of an objective pathologic feature, such as mean mitotic activity, is also useful in selecting patients for future systemic neoadjuvant or adjuvant trials and primary therapy.