Abstract: Objective:To analyze the consistency of HER- 2 expression among endoscopic biopsy and radical operation specimens of gastric adenocarcinoma and to investigate the clinical application value of HER-2 detection in trastuzumab treated patients. Methods: From March 2013to February 2014, 167 patients from Shanghai Changhai Hospital were diagnosed with gastric adenocarcinoma using endoscopic biopsy specimens. The corresponding surgical specimens were collected for pathological analysis. The relevant clinical and pathological data were collected. HER- 2 protein expression of endoscopic biopsy specimens was detected by immunohistochemistry (IHC). HER- 2 protein expression and gene amplification status of the corresponding tumor resection specimens were detected by IHC and fluorescence in situ hybridization (FISH). Results were analyzed for clinicopathological characteristics. Results:Among the 167 cas-es,18cases ( 10. 8%) were HER-2 positive, including 10cases showing IHC 3 + and 8 cases showing IHC 2 + with FISH positive. The consis -tency rate result among endoscopic biopsy and surgical operation specimens was 82% . Excluding the cases showing IHC 2 + , the true positive rate and the true negative rate were 73. 3% and 97. 0%, respectively.Conclusion: HER- 2 detection of endoscopic biopsy speci-men by IHC shows great predictive value. The main reason for the difference of surgery and biopsy specimens is the heterogeneity of tumor expression. Increasing the number of specimens and combined testing with FISH are important methods to reduce misjudge -ment.