Effects of cheonggukjang on immunohistochemical reactions in gastrointestinal (GI) tract of rats were investigated. $CD4^+/CD8^+$ immunoreactive cells of cheonggukjang-fed diet groups were more strongly stained in lamina propria of mucosa and submucosa than those of basal diet group. Universal nitric oxide synthase immunoreactive density in colon was mildly stained in surface epithelium and mucous secretory gland, and strongly stained in submucosa and myenteric plexus in muscle layers of all cheonggukjang-fed diet groups. Protein kinase C-${alpha}$ immunoreactive cells in colons of 15 and 25% cheonggukjang-fed diet groups were more strongly stained in mucosa, submucosa, and muscle layers than those of basal diet group. These results indicate mucosal immune activity, gastrointestinal motility, blood circulation, and physiological activities of enteroendocrine cells in GI tract could be increased with cheonggukjang intake.