Objective: The aim of this study was to identify the clinical features and prognostic factors associated with ex-tremity osteosarcoma with pathologic fracture. Methods: The clinical records of 271 patients with extremity osteosarcomas were retrospectively reviewed. The data obtained covered the period from October 2003 to May 2012, and included sex, age, tumor site etc. The mean fol ow-up time was 25.2 months (ranged from 1 to 117). Chi-square method and Kaplan-Meier method were used to compare clinical dif erences and overal survival between patients with or without pathologic fracture, re-spectively. The univariate analysis was used to determine the prognostic factors related with survival rate by log-rank test. The multivariate analysis of prognosis was performed by COX proportional hazards regression model. Results: The proportions of patients having a tumor’s diameter of 10 cm or more (P = 0.038), locating upper limbs (P = 0.004) and receiving amputa-tion surgery (P = 0.02) were significantly higher with pathological fracture group than without pathological fracture group. The local recurrence rate (P = 0.000) was also significantly higher in the pathological fracture group. The median survival time of patients with or without pathological fracture was 16 (95% confidence interval: 14.6-17.4) months and 22 (95% confidence interval: 19.8-24.1) months (P = 0.002). The Log-rank univariate analysis indicated that the tumor size, Enneking’s surgical staging, Karnofsky performance status (KPS) score, cycles of adjuvant chemotherapy, local recurrence and metastasis were significantly related to overal survival. Multivariate Cox regression analysis revealed KPS score, cycles of adjuvant chemo-therapy and metastasis were independent prognostic factors (P < 0.05). Conclusion: Compared with the patients without pathological fracture, a higher proportion of patients receiving amputation surgery or having larger tumor size, humeral os-teosarcoma or local recurrence was observed in patients with pathological fracture, and the prognosis of these patients was poor. The independent prognostic factors of extremity osteosarcoma with pathologic fracture were the KPS score, cycles of adjuvant chemotherapy and metastasis.