Midkine (MK), a heparin-binding growth factor,can regulate cell growth, survival and differentiation. MK is expressed at high levels in a variety of human carcinomas. Recently, the urine and serum MK concentration was analyzed in gastric cancer patient. However, the association of the cytokine mRNA expression with the categorical clinicopathological variables of the tumors and the location of its protein expression in the tumor tissues are still elusive. MK mRNA expression from the surgically resected specimens of healthy gastric tissues (9 cases), gastric cancer tissues and the matched non-cancerous tissues adjacent to the cancer (37 cases) were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR) and real-time PCR. Immunohistochemical analysis was performed to locate MK in gastric cancer. The expression of MK mRNA in gastric cancer was much higher in tumor tissues than that in the non-cancerous tissues and control tissue samples. And its expression was significantly associated with the pTNM stage and distant metastasis, but not with the differentiation grade, tumor size and nodal involvement. MK protein was ubiquitous in the tumor, especially in the adenoid part of tumors. In addition, it was found in the cytoplasm of tumor cells and highly concentrated in nucleus and nucleolus. The expression level and location of MK in gastric tumor tissues of Chinese Patients may be related to the tumor genesis and progression. Further study is necessary on the mechanism of MK in gastric tumorigenesis and tumor growth.