Matrix metalloproteinase (MMP) expression is associated with advanced-stage cancer and contributes to tumor progression, invasion, and metastasis. Membrane type matrix metalloproteinase (MT-MMP) has a potential transmembrane domain at the C terminus and activates pro-MMP-2, which is mainly produced from interstitial fibroblasts. Its expression on the membrane of invasive tumor cells results in the pericellular space degradation at cell-matrix contact sites and renders cancer cells more invasive at the migration front. To elucidate the relationship between MT-MMP expression and metastasis and prognosis in gastric cancer patients, MT-MMP expression was analyzed immunohistochemically in 127 primary tumors and results were correlated with several prognostic parameters and patient's survival. MT-MMP immunoreactivity was stained on the cell membrane of cancer cells and fibroblasts in the invasion front. MT-MMP was detected in 72 tumors (57%) (MT-MMP-positive). MT-MMP expression was closely associated with macroscopically invasive type, nodal involvement, lymphatic invasion, vessel invasion, and peritoneal dissemination. Patients with MT-MMP-positive tumor had a significantly worse prognosis than those with MT-MMP-negative tumor (p<0.001). Multivariate analysis showed MT-MMP overexpression as an independent prognostic factor in gastric cancer patients. Immunohistochemical analysis for MT-MMP may be an indicator of metastatic potential or the prognosis of gastric cancer patients.