This study was designed to examine whether or not phospholipid is contained in the secretory granules of the rat palatine gland acinar cells, and if present, to examine the movements of phospholipid in the secretory granules during postnatal development. The palatine glands of male Wistar rats aged 0 to 56 days were used. Acid-hematin staining showed a few positive acinar cells with a faint reaction in the acini on day 0, numerous positive cells with an intense reaction on day 7, a weakening reaction in the cells on day 14, and almost no reactivity on day 35 and after. In contrast, alcian blue staining showed acinar cells with a weak reaction on day 7, a gradual increase in the reaction from day 14, and the presence of many cells with an intense reaction on day 28 and after. Electron probe microanalysis (EPMA) revealed a higher density of phosphorus in samples on day 7 than on day 56. These findings suggest that developing rat palatine gland acinar cells contain phospholipid in the secretory granules, being particularly more conspicuous around postnatal day 7, but that the amount of phospholipid decreases as the cells change to mature mucous cells.