Presence of pancreatic alpha-amylase, trypsinogen, and lipase in normal pancreatic ducts was evaluated immunohistochemically in 10 surgically resected normal pancreatic specimens, using monoclonal antibodies against human pancreatic alpha-amylase, trypsinogen, and lipase. Immunoreactivity to all enzymes occurred patchily in some epithelial cells not only of the common bile duct and its periductal glands but also of the main and interlobular pancreatic ducts and periductal glands in the main pancreatic duct, as well as in pancreatic acinar cells. Ductal staining was fine-granular, and generally present in the supranuclear cytoplasm. Immunoreactivity was abolished by preabsorption. Centroacinar cells and intercalated and intralobular pancreatic ducts did not stain for any enzyme. These findings suggest that some epithelial cells of the large-sized pancreatic duct and its periductal glands express pancreatic alpha-amylase-, trypsinogen-, and lipase-like peptides, as do some epithelial cells of common bile duct and its periductal glands.