Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) is selectively expressed in the endothelial cells of intestinal mucosa and gut-associated lymphoid tissue (GALT). Engagement of MAdCAM-1 to its ligand, integrin alpha4beta7, on lymphocytes is associated with the homing of gut-associated lymphocytes to normal gastrointestinal tract and inflammation sites. The present study was designed to elucidate differences between Crohn's disease (CrD) and ulcerative colitis (UC) from the expression patterns of MAdCAM-1. Samples were taken from 40 patients with CrD and 24 patients with UC at surgical resection. Using frozen sections, immunohistochemistry was performed for MAdCAM-1, E-selectin and CD34. MAdCAM-1+ venules were abundant in inflamed mucosa in both UC and CrD. In contrast, clear differences were noted between UC and CrD in the inflammatory area in the ulcer base, that is, MAdCAM-1+ venules were more abundant in CrD than in UC (P < 0.001), while E-selectin was expressed equally in these venules in both diseases. Furthermore, CrD was characterized by the occurrence of MAdCAM-1+ venules in deeper layers of the intestinal tissue, mainly in lymphoid aggregates. Our data indicated more extensive expression of MAdCAM-1 in CrD, which could contribute not only to mucosal inflammation, but also to transmural inflammation in CrD.