Matrix metalloproteinases (MMPs) have been implicated in the invasion and metastasis of tumor cells. To elucidate the involvement of MMP-1 in human pancreatic ductal adenocarcinoma, we performed immunohistochemical analysis on tissues from 2 fetal pancreases, 5 normal pancreases, 6 cases of chronic pancreatitis, and 46 pancreatic ductal adenocarcinomas. In addition, among the pancreatic carcinomas, we compared MMP-1 expression in relation to the degree of differentiation, lymph node metastasis, and depth of invasion of the carcinoma. MMP-1 was expressed faintly in fetal and normal pancreatic tissues. Among the 46 pancreatic carcinomas, 33 (72%) showed positive staining for the MMP-1 protein. There was no difference in the degree of differentiation. In situ hybridization confirmed the presence of MMP-1 mRNA in the pancreatic carcinomas. Expression of MMP-1 mRNA was also detected in two human pancreatic carcinoma cell lines and three pancreatic carcinoma tissues by the reverse transcription polymerase chain reaction method. MMP-1 was expressed in the carcinoma cells themselves and in stromal fibroblasts. Patients with MMP-1 positivity in the primary site had a significantly poorer prognosis than patients who were MMP-1 negative (P < .05). MMP-1 expression, however, had no relation to the presence of lymph node metastasis, tumor size, or tumor-node-metastasis stage in pancreatic carcinomas. These findings suggest that MMP-1 expression is related to the carcinogenesis and prognosis of human pancreatic ductal adenocarcinoma.