ObjectiveTo study the expression of matrilysin in gastric cancer and to evaluate the correlation between its expression and invasion, metastasis, and prognosis. MethodsA total of 52 patients with gastric cancer were selected and followed up. The expressions of matrilysin in gastric primary focus, normal gastric mucosa, and metastatic lymph nodes were examined by reverse transcriptionpolymerase chain reaction (RT-PCR), Western blot, and immunohistochemistry, respectively. The correlations between matrilysin expression and tumor invasion, metastasis, and prognosis were assessed. ResultsThe expressions of matrilysin in gastric primary focus and metastatic lymph nodes significantly increased, while decreased or loss in normal gastric mucosa (Plt;0.001). The higher concordance was seen between the levels of mRNA and protein (Plt;0.001). Among patients with infiltrating type, penetrated serosa, area of serosa involved more than 20 cm2, and metastatic lymph nodes more than 7, the expression of matrilysin was significantly higher (Plt;0.01). The survival rate of patients with matrilysin higher expression (34.1%) was significantly lower than that with matrilysin lower expression (55.6%), χ2=9.778， P=0.002. Conclusions Up-regulated expression of matrilysin plays an important role in tumor invasion, metastasis, and poor prognosis, and it is a good molecular marker to reflect the biological behaviors of gastric cancer.