Pancreatitis-associated protein (PAP) is a lectin-related protein barely detectable in normal pancreas but overexpressed by this tissue during the acute phase of the pancreatitis. We describe in this report that PAP is constitutively expressed in the human intestinal tract. Northern blot analysis with pancreatic cDNA as probe shows the presence of a transcript in the jejunum that has the same electrophoretic mobility as the pancreatic mRNA. No signal was detected in colon, however. In addition, immunoblotting assays, utilizing specific rabbit immunosera prepared against PAP, revealed the presence of a protein of 16,000 Da (as in pancreatic juice) in the homogenate of jejunum, but not of the colon. When the same antibodies were used for tissule localization of the protein, positive immunoreactivity was observed on Paneth cells and in some goblet cells located in jejunum at the bottom of the crypts. No staining was observed in colon.