The purpose of this study was to clarify the morphologic characteristics of the crypt cells in the small intestine. Electron microscopic studies were performed on the ileum of the mouse at 6 and 20 hours after salmonella typhimurium infection. The granule-containing cells of exocrine type in the ileal crypt were composed of four main cell types: Paneth cell, mucous cell, granular mucous cell, and intermediate cell. Among these cells, Paneth cells contained spherical granules, 1~3 micrometer in diameter, with centrally located large dense core and narrow electron lucent halo. The granules of the intermediate cells were large spherical, 1~2 micrometer in diameter, and consisted of dense core and wide halo with moderately dense and finely granular matrix materials. At 6 hours after salmonella typhimurium infection, notable changes were observed in the cells of some intestinal crypts. Most of the crypt cell contained granules consisting of electron dense core and wide halo. These granules are resembled those of intermediate cells in appearance. Some cells secreted the granules by exocytosis. At 20 hours after salmonella typhimurium infection, the crypt was composed of paneth cell, intermediate cell, and a cell containing granules of found in paneth cell and intermediate cell.