Objective: To evaluate X-linked inhibitor of apoptosis protein (XIAP) expression in biopsy specimens from the patients with stage IIB osteosarcomas before chemotherapy to study XIAP expression and its predictive significance of prognosis in stage IIB osteosarcomas. Methods: The expression of XIAP was retrospectively detected by SP immunohistochemistry in 31 cases biopsy specimens from stage IIB osteosarcomas before chemotherapy, and the relationship between XIAP expression and clinicopathologic features of the patients with stage IIB osteosarcomas was analyzed. Results: The osteo-sarcoma specimens showed strong cell nucleus immunoreaction of XIAP while normal bone specimens showed weak. High XIAP positive expression independently predicted the patient’s poor outcome and had no relationship with clinicopathologic variables such as age, gender, location, tumor size, rate of tumor necrosis to preoperative chemotherapy, local recurrence (P > 0.05). Significant correlations were found between high XIAP expression and metastasis (P = 0.022), and also between high XIAP expression and final survival (P = 0.011). Conclusion: XIAP plays an important role in the development of stage IIB osteosarcomas and XIAP expression of biopsy specimens before chemotherapy can be seen as a promising prognostic marker in early predicting the outcome of patients suffering from stage IIB osteosarcomas. Objective: To evaluate X-linked inhibitor of apoptosis protein (XIAP) expression in biopsy specimens from the patients with stage IIB osteosarcomas before chemotherapy to study XIAP expression and its predictive significance of prognosis in stage IIB osteosarcomas. Methods: The expression of XIAP was retrospectively detected by SP immunohistochemistry in 31 cases biopsy specimens from stage IIB osteosarcomas before chemotherapy, and the relationship between XIAP expression and clinicopathologic features of the patients with stage IIB osteosarcomas was analyzed. Results: The osteo-sarcoma specimens showed strong cell nucleus immunoreaction of XIAP while normal bone specimens showed weak. High XIAP positive expression independently predicted the patient’s poor outcome and had no relationship with clinicopathologic variables such as age, gender, location, tumor size, rate of tumor necrosis to preoperative chemotherapy, local recurrence (P> 0.05). Significant correlations were found bet ween high XIAP expression and metastasis (P = 0.022), and also between high XIAP expression and final survival (P = 0.011). Conclusion: XIAP plays an important role in the development of stage IIB osteosarcomas and XIAP expression of biopsy specimens before chemotherapy can be seen as a promising prognostic marker in early predicting the outcome of patients suffering from stage IIB osteosarcomas.