The pain, swelling of salivary glands and dry mouth are not infrequent complication of the high dose radioiodine treatment in the patients with differentiated thyroid cancer. The purpose of this study was, by the dynamic salivary scintigraphy, to observe the change of the salivary function after the high dose $(150sim200mci)$ radioiodine treatment. From May 1987 to April 1988, the dynamic salivary scintigraphy with 5mci of $^{99m}Tc-pertechnetate$ and gamma camera was performed before and 7 days after the radiolodine treatment in 7 patients with differentiated thyroid cancer. Just after the dynamic scintigraphy, the stimulation test with vitamin C solution of pH3.0 and poststirnulation scintigraphy were done, and the radioactivity uptake index, excretion fraction and salivary clearance after the stimulation were calculated for each gland. There was positive correlation between the radioactivity uptake index and excretion fraction after the stimulation. The salivary clearance after the stimulation was $18.96{pm}8.95ml/min$ in the pretreatment state, and $14.37{pm}7.7ml/min$ after the radioioine treatment. After the radioiodine treatment, the radioactivity uptake index, excretion fraction and salivary clearance after the stimulation were significantly reduced in the parotid glands, but only the excretion fraction was reduced in the submandibular glands. The more the pretreatment salivary clearance after the stimulation was, the % change after the treatment was smaller. Further studies on the relation between the radiation dose in the salivary glands and the change of their function, and the long-term observation for the recovery of function are expected.