Type IIbeta-hydroxysteroid dehydrogenase endows specificity on the mineralocorticoid receptor by metabolizing cortisol and regulates sodium absorption in renal and colonic epithelium. Altered expression of this enzyme may be associated with impaired sodium absorption often seen in colonic mucosa of inflammatory bowel disease. The aim of this study was to investigate possible abnormality of 11beta-hydroxysteroid dehydrogenase protein and mRNA expression in inflammatory bowel disease. In Crohn's disease, the colonic epithelium showed comparable levels of immunoreactivity and mRNA expression to those of control, except for the decreased immunoreactivity in severe inflamed lesions with deep ulcer. In contrary, a lack or decrease of immunoreactivity was relevant in ulcerative colitis regardless of the histological degree of inflammation. The mRNA expression was also significantly decreased in ulcerative colitis. This study demonstrates that abnormality of epithelial cells in ulcerative colitis includes the enzyme that regulates water and sodium absorption, which are physiologically essential.