Abstract: Objective: To investigate the expression and prognostic significance of insulin-like growth factor binding protein 5(IGFBP5) in gastric adenocarcinoma (GAC). Methods: IGFBP5 expression in tissue samples from 236 GAC patients was analyzed using immunohistochemical methods. These patients had undergone surgical resection between 20003 and 2006 in Sun Yat-Sen University Cancer Center. The relationship between IGFBP5 expression and clinicopathological factors in the 236 GAC patients was analyzedusing Pearson correlation analysis. The significance of IGFBP5 in predicting the survival status of these patients was analyzed using Kaplan–Meier survival analysis and Cox's proportional hazards regression model. Results: Immunohistochemical staining data indicatedthat IGFBP5 expression was significantly decreased in 159 of the total GAC cases (67.4%). Of the 62 cases with well- and moderatelydifferentiated GAC, 31 (50%) exhibited reduced IGFBP5 expression. Of the 174 cases with poorly differentiated GAC, 128 showed reduced IGFBP5 expression. Reduced IGFBP5 expression was also observed in female patients and in patients with tumors over 5 cm insize or with poorly differentiated tumors (P<0.05). The reduced expression of IGFBP5 was common in the tumors that were staged asT3+4a/b and Ⅲ/Ⅳ (P<0.05). Kaplan-Meier survival analysis revealed that the reduced expression of IGFBP5 was associated with poorprognosis in GAC patients (P<0.001). Cox regression analysis identified IGFBP5 expression as an independent prognostic factor for theoverall survival of these cancer patients (HR=1.897, P=0.029). Conclusion: IGFBP5 expression is reduced in GAC tissues, andIGFBP5 independently predicts an unfavorable prognosis in GAC patients.