Morphological and histochemical methods revealed cells intermediate between mucous neck cells and chief cells in rat stomach. The secretory granules of mucous neck cells and chief cells were homogeneous. However, some cells resembling mucous neck cells in shape and size yet contained heterogeneous granules. One type of cell contained mucous granules showing a bipartite structure. The inner cores of these granules resembled the granules of mucous neck cells morphologically and after staining by the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) procedure and lectin-ferritin methods. The outer layer of these granules, however, resembled the granules of chief cells and failed to stain by these methods. Another type of cell also contained bipartite granules, but these showed a dense cap and lucent matrix. The cap of the granules did not stain with the PA-TCH-SP and lectin methods, but the remaining matrix was reactive. These presumed transitional cells were located in a layer between the mucous neck cells and the chief cells. Immature chief cells with sparse granular reticulum were found near these intermediate cells in some cases. Many similar intermediate type cells were also found in early developmental stages of the gastric mucosa in rat. These results suggest a close relationship between chief cells and mucous neck cells; chief cells may develop from undifferentiated stem cells via mucous neck cells in adult rat stomach.