【Abstract】 Objective This study was to evaluate the HER2 gene status and to investigate the relationship between the expression/gene of HER2 and the clinicopathological characteristics of gastric carcinomas. Methods One hundred and seventy cases including the clinical and pathological information of primary gastric or gastroesophageal junction adenocarcinomas diagnosed and treated surgically from January to March, 2009 at the West China Hospital were enrolled in the study. Automated immunohistechemistry(IHC) staining and FISH were carried out to detect the HER2 status，respectively. Result Among the 170 cases, HER2 overexpression showed 100 cases (588%) 0+，33 cases (194%)1+，14 (82%)2+，23 (136%)3+ by IHC. 27 cases (159%) showed HER2 gene amplification by FISH. 20 cases（704%）showed chromosome 17 polysomy. Four(4%) of the 100 cases negative (0 or 1+) by IHC showed amplification by FISH, whereas 14 (378%) of the 37 cases with HER2 protein overexpression showed HER2 nonamplification by FISH. The correlation between IHC and FISH results was statistically significant (P＜001). HER2 gene amplification and HER2 protein overexpression was not correlated with the age and sex of patients, and tumor size, location, pathological and TNM stage, but with a wellor moderately differentiation according to the World Health Organization classification (P＜001) and in cases of intestinal type by the Lauren classification (P＜001)).Conclusion HER2 overexpression and HER2 gene amplification was 217% and 159% respectively. The higher difference, the more frequence of overexpression/amplification. At the same time, the positive cases were major in intestinal type with high incidence of chromosome 17 polysomy. To make a definite diagnosis of HER2 positive cases in gastric cancer, IHC was the initial testing method, FISH as a significant detection method.