In situ hybridization and immunocytochemical techniques were employed to examine the expression of matrix metalloproteinases-1 (MMP-1) and to identify the pattern of its distribution in rat pancreas. The results indicated that the signal of MMP-1 mRNA and MMP-1 positive immunoreaction were detected in some fiberoblasts around interlobular ducts and exocrine cell in margin acinus of some lobules, but the signal of MMP-1 mRNA and MMP-1 positive immunoreaction could not be detected in most of other acinus and islets of pancreas. It is concluded that the expression of MMP-1 in above cells of rat might play an important role in acinar proliferation and differentiation of rat pancreatic tissues.