Objective: To study the expression and clinical significance of Notch1 and human epidermal growth factor receptor 2(HER2) in gastric carcinoma. Methods: The expression of Notch1 was detected by immunohistochemistry,and assessment of HER2 protein overexpression and gene amplification were done by immunohistochemistry and fluorescence in situ hybirdizaton(FISH) in tissue microarrays containing 317 gastric carcinomas and relatively normal gastric mucosa tissue. Results: Overexpression of HER2 protein was observed in 64 cases(20.2%) and HER2 gene amplification was detected in 58 cases(18.3%) of gastric carcinoma. The concordance rate between the immunohistochemistry and FISH was 89.1%. HER2 protein overexpression and gene amplification were significantly associated with tumor location and the Laurén’s classification(P < 0.01),but not with differentiation grade and clinical stage (P > 0.05). The expression of Notch1 protein was observed in 197 cases (62.1%) of gastric carcinoma,and was significantly associated with differentiation grade and clinical stage(P < 0.05). The expression of Notch1 was negatively correlated to the protein overexpression and gene amplification of HER2 (r = -0.191,P < 0.01;r = -0.169,P < 0.01,respectively). Conclusion: The significantly dys-regulated expression of Notch1,which could promote growth and invasion of gastric carcinoma cells and correlated to the higher clinical TNM stage,was observed in gastric carcinoma. The expression of Notch1 negatively correlated to the protein overexpression and gene amplification of HER2 suggests that Notch1 may act as a novel therapeutic target molecule for gastric carcinoma.