Objective: To investigate the expression of Bmi-1 (B-cell specific moloney leukemia virus insertion site 1) in gastric cancer tissues and its relation with the clinicopathological factors of gastric cancer. Methods: RT-PCR and Western blot analysis were performed to detect the expression of Bmi-1 in 44 cases of gastric cancer tissues and their adjacent normal tissues. Results: The positive rate of Bmi-1 mRNA expression in gastric cancer tissues was 72.73%, which was significantly higher than that in the adjacent normal tissues (14.3%) (P＜0.05), and the expression of Bmi-1 protein in gastric cancer tissues was also significantly higher than that in adjacent normal tissues (P＜0.05). The expression of Bmi-1 in patients with lymph node and distant metastases was significantly higher than that in patients without lymph node and distant metastases (P＜0.05). The expression of Bmi-1 was irrelevant to the sex, age, tumor size or degree of tumor differentiation of the patients, because no significant differences between the groups divided according to these four factors were obtained (P>0.05). Conclusions: The elevated expression of Bmi-1 may possibly be involved in the occurrence, invasion and metastasis of gastric cancer.