Lysozyme and lactoferrin, substances of the non-specific defense system of the salivary glands, were studied in normal human parotid glands of neonates and adults using the immunoperoxidase method. To our knowledge, the immunohistochemical detection and distribution of lysozyme and lactoferrin in neonate parotid glands have not been previously reported. In neonate parotid glands, a monotonous positive reaction for lysozyme was found in the acini, in the intercalated ducts and in a few cells of large ducts. On the contrary, lysozyme was observed mainly in the intercalated ducts of the adult parotid glands. Three staining patterns for lactoferrin were found in neonate parotid glands. The first pattern was identical to that of lysozyme in neonates, the second was similar to that of lactoferrin in adults, and in the third extremely few acinar and intercalated duct cells were positive. In adult parotid glands, lactoferrin was detected in groups of acini and intercalated ducts and rarely striated duct cells. In adult parotid glands, our findings are discussed in correlation with those of other investigators. The results of our study indicate that lysozyme and lactoferrin have an important role in the defense mechanism of neonate parotid gland. There is also a distinct immunohistochemical difference between neonate and adult parotid gland. Since it is known that there is a morphological differentiation of the parotid gland postnatally, it is presumably suggested that an immunohistochemical differentiation also occurs.