This study was performed to observe the irradiation effects on the salivary gland, sixty Sprague-Dawley rats, weighing approximately 250 gm±10 mg each were divided in three groups ; control group(12 rats) did not received irradiation, another group(24 rats) received irradiation with 1800 cGy in single dose, the other group received irradiation with 2700 cGy in single dose. Histopathologic change of the salivary glands were examined by light and transmission electron microscope at 1 day, 3 days, 7 days, 14 days, 28 days, and 56 days after irradiation. The summarys were as follows ; 1) Light microscopic change of serous acini after irradiation was pyknosis of nucleus, atrophy of acini, vacuolization of cytoplasm, decreased numbers of scretory granules in the cell, intercellular infiltration of inflammatory cells and proliferation of collagen fibers. 2) Electron microscopic change was pyknosis of nucleus, hypertrophy of Golgi complex, destruction of cristae and expension of mitochondria, distorsion of rough endoplasmic reticulum and decrease of secretory granules were observed. 3) The excretory duct displayed no significant alteration. 4) The salivary glands showed the most extensive damage on the 7th day after irradiation of 1,800 cGy and it was slowly recovered from the 14th day of irradiation. 5) The group irradiated with 2,700 cGy showed more serious damage than the group irradiated with 1,800 cGy and it showed the greatest injury from the 3rd day after irradiation and recovered slowly from the 28th day.