Abstract: Objective : To investigate correlation between the expression of hMSH2, p53 and of PCNA and its significance in gastric cancer. Methods : Immunohistochemistry SP method was used to examine expression of hMSH2, p53 and of PCNA in gastric cancer, adjacent mucosa and gastriticmucosa. Results : a) The positive rates of all the three gene expressions in cancerous tissue were higher than those in non-cancerous tissue. Among them, the positive rates of p53 and PCNA in poor differentiated cancer as well as in cancerous tissue with lymph node metastasis were both higher than those in well differentiated cancer as well as in cancerous tissue without metastasis (P<0.05); b) Expression of hMSH2 and PCNA as well as expression of p53 and PCNA both correlated positively (P<0.05). Conclusion : Abnormal expression of hMSH2, p53 and PCNA as well as interaction between hMSh2 and PCNA may contribute to carcinogenesis of gastric cancer.