Abstract: Objective : To investigate the expression of MCL1 protein in gastric carcinoma and to explore the relation-ship between MCL1 protein expression and the development of gastric carcinoma. Methods : Expression ofMCL1 protein was examined immunohistochemically by the streptavidin-peroxidase conjugated method (SP)in normal mucosa, paracancerous tissues and gastric carcinoma. Western blot was used to detect the expres-sion of MCL1 protein in BGC823, SGC7901 and MKN28 gastric cancer cell lines. Results : MCL1 protein ex-pression was located in the cytoplasm. The positive rate of MCL1 protein expression was 18.18% (4/22) innormal gastric mucosa, 54.17% (26/48) in paracancerous tissues, and 83.33% (75/90) in gastric carcinomatissues. The positive rate of MCL1 protein expression in gastric carcinoma was significantly higher than that inparacancerous tissues ( P <0.05). The positive rate of MCL1 protein expression in tissues adjacent to carcino-ma lesions was significantly higher than that in normal gastric mucosa ( P <0.05). MCL1 expression rate was93.48% (43/46) in tissues from carcinoma patients with lymph node metastases and 72.72% (32/44) in thosewithout lymph node metastases, with a significant difference ( P <0.05). No correlation was found betweenMCL1 protein expression and gender or age. The expression of MCL1 was negatively correlated with the dif-ferentiation of gastric carcinoma. Conclusion : MCL1 protein expression is related to the carcinogenesis, differ-entiation and lymph node metastasis of gastric carcinoma.