Purpose: To assess the functional change of salivary gland, recovery of salivary destruction, difference of susceptibility to irradiation between the parotid and submandibular gland, correlation between the xerostomia and excretory rate by irradiation in salivary Tc-99m- pertechnetate in patients with head and neck cancer. Materials and Methods: We evaluated 19 patients with head and neck cancer who Tc-99m-pertechnetate salivary gland scan before, during and after radiotherapy. We measured the uptake of radioactivity every 5 minutes for 60 minutes after injection of Tc-99m- pertechnetate(370MBq). We also evaluated the first excretory function stimulated by 5% citric acid at 30 minutes after injection of Tc-99m-pertechnetate and then the second excretory function stimulated by 10% citric acid at 45 minutes. Results: The mean uptake curves showed a sharp increase at the 1st week of radiotherapy and then showed a gradual decrease afterwards during radiotherapy. And the mean uptake curves after radiotherapy persistently decreased on follow up scans without being recovered. The excretory rates decreased gradually as radiation dose increased and were not recovered after radiotherapy. Our study was not satisfactory enough to show the difference of susceptibility to irradiation between the parotid and salivary gland and the correlation between the symptom of xerostomia and the change of the excretory rates. Conclusion: The parotid and submandibular gland scans using Tc-99m- perechnetate are useful in the assessment of the functional change of the salivary gland by radiotherapy and predicted the functional change of the salivary gland until 1 year-follow up scan. KW: Salivary gland abnormality, Salivary gland, radionuclide studies, Salivary gland, therapeutic radiology, Tc-99m-pertechnetate