To elucidate the role of intercellular adhesion molecules (ICAMs), which has not been well understood in pancreas, we investigated the localization and expression of ICAM-1 by immunohistochemistry and in situ hybridization (ISH) in pancreatic adenocarcinoma and in normal pancreas. The localizations of ICAM-2 and ICAM-3 were also investigated by immunohistochemistry. In normal pancreas, acinar cells, duct epithelial cells, and Langerhans islet cells failed to stain with anti-ICAM-1, anti-ICAM-2, and anti-ICAM-3 antibodies. These cells showed no expression of ICAM-1 mRNA. On the other hand, various percentages of carcinoma cells were stained with anti-ICAM-1 antibody, while no carcinoma cells were stained with anti-ICAM-2 and anti-ICAM-3 antibodies. ICAM-1 mRNA expression was also observed in carcinoma cells, and ICAM-1 mRNA expression was associated with localization of the ICAM-1 protein. These results suggest that ICAM-1 expression is up-regulated in pancreatic adenocarcinoma cells and that ICAM-1 is involved in malignant processes in pancreas.