In the present study, we used in situ hybridization to study 36 primary hepatocellular carcinomas (HCCs) and 35 pancreatic adenocarcinomas to analyze the expressions of membrane-type 1 matrix metalloproteinase (MT1-MMP), MMP-2, and MMP-9 mRNAs. In HCCs, MT1-MMP mRNA was mainly expressed by cancer cells and to a lesser extent by stromal cells. MMP-2 mRNA was expressed predominantly by cells of tumor stroma, whereas MMP-9 mRNA was seen mainly in neoplastic epithelial cells. In pancreatic adenocarcinomas, MT1-MMP and MMP-9 mRNA were seen at moderate levels both in cancer and in stromal cells, whereas MMP-2 mRNA was predominantly expressed by the tumor stroma. Antigens of MMP-2, MMP-9, and MT1-MMP immunolocalized to the neoplastic epithelium and to the stromal cells in both tumor types. In gelatin zymography, increased amounts of latent and active MMP-2 were found in tumor samples of HCC as compared with adjacent nontumorous liver tissue. On the other hand, the latent form of MMP-9 was found in almost equal amounts both in tumor and normal liver samples, but its active form was present only in HCC. Expression of MT1-MMP mRNA had a tendency to be associated with a lower degree of differentiation in HCC, but such association was not noticed in pancreatic tumors. Correlation to the clinical data showed that MT1-MMP expression had a strong statistical association with a poor outcome of patients (P < 0.01). A similar tendency was also observed in pancreatic adenocarcinomas, but the association did not reach statistical significance. MMP-2 and MMP-9 mRNA expression did not have significant correlation with prognosis. The results of this study support the previous suggestions of the importance of MT1-MMP for malignant growth and indicate that increased MT1-MMP mRNA expression by tumor cells in HCCs and pancreatic adenocarcinomas may have prognostic significance.