Proteins' expression of tight junction proteins in rat small intestine was analyzed by means of immunohistochemistry and Western blotting. Claudins -1, -2, -3, -4, -5, -7 and occludin were analyzed. Confocal laser-scanning microscopy revealed differences in the subcellular distributions of these proteins. Claudins-1, -2, -3, -4, -5, and -7 were localized within the tight junction complex and were also detectable in subjunctional regions. Distributed subcellular localization of these proteins may reflect their different roles during formation of epithelial cell layers as well as in paracellular transport of ions in the small intestine.