To investigate the effect of amifostine, we administered amifostine, a radioprotective agent, 30 minutes before exposing the maxillary region of mice, including the parotid gland, to 5 Gy or 10 Gy X-ray irradiation. The survival rate was recorded, and changes in the parotid gland morphology were investigated by examining the hematoxylin and eosin (HE)-stained specimens and light microscope autoradiography (LMARG) images obtained 30 days after irradiation. A survival rate of 100% was not observed in any group administered 200 mg/kg amifostine with or without irradiation. Among the groups irradiated with 10 Gy X-rays, the survival rate was higher and the survival period was longer in the 100 mg/kg amifostine group than in the no amifostine group. The histological findings in the group that received 5 Gy irradiation without amifostine were as follows: auxetic growth of acinar cells, nuclei of all sizes, cells in the mitotic phase, and cells undergoing apoptosis. Further, the treated groups were compared with the no amifostine and no irradiation group (untreated control). LMRG imaging revealed that the number of reduced silver grains per mm² of acinar cells after 30 min of ³H-leucine administration was higher than that after 120 min in mice treated with 100 mg/kg amifostine with or without 5 Gy irradiation. This observation was similar to that in the untreated control.This finding suggests that although amifostine administration reduces the adverse effects of irradiation on the parotid gland, higher doses of amifostine may be fatal.