Background: The rat parotid gland is ectodermal in origin and originates from two adjacent embryonic tissues, the epithelium and mesenchyme. It is immature at birth and its differentiation is completed postnatally. Aim of the work: The work aims to know the postnatal developmental changes of the parotid gland in albino rats aged one day to old age using light and electron microscope study. Material and Methods: Twenty pregnant wistar albino rats were obtained from animal house, faculty of veterinarian medicine. After delivery their offspring were divided into six groups; five rats/group males and females. Group I: rats aged one day, Group II: rats aged one week, Group III: rats aged two weeks, Group IV: rats aged three weeks (age of weaning), Group V: rats aged three months (adult age) and group VI: rats aged two years (old age). At the exact ages of study, the rats were anaesthetized with ether inhalation and sacrificed. The parotid glands were removed and processed for light and electron microscopic examination. Results: The histological study revealed that, the gland began its development as immature acini and ducts. More differentiation to all compartments had occurred. There wasan increase in the cell numbers of acini, intercalated ducts, striated ducts and excretory ducts till the adult age then decreased in old age. The stromal cells showed a continuous increase up to the old age. Alpha smooth muscle actin increased till the age of two weeks then grdually decreased from the three weeks to the old age.The ultra-structural features revealed that, thesecretorygranules changed from completely mucous granules of low electron density in rats aged one week to completely serous granules of high electron density. Lipofuscin granules and lipid droplets were very characteristic to the old age. Conclusion: The rat parotid gland is immature at birth and completes its development postnatally. The secretory granules completely changed from mucous to serous at the age one week. Key words: Parotid, Granules, Development, Myoepithelial cells