Background: Common types of the benign thyroid nodules are nodular hyperplasia and lymphocytic thyroiditis (LT). Many clinicians have been experienced that euthyroid LT progress to hypothyroidism or thyroid cancer. The present study aims to decide the follow up period of LT patient. Methods:?We retrospectively reviewed the data of patients who had underwent ultrasound-guided FNAC on thyroid nodule from January 2005 to December 2010 at our center. we selected 289 patients had underwent ultrasound guided FNAC and pathologically diagnosed with thyroiditis. Finally 109 patients had follow-up data of TFT or thyroid US. Results:?Over the mean follow-up duration of 51.6 months, among the 109 patients 88 showed normal TSH.14 of 109 patients developed to clinical hypothyroidism.Mean duration to primary endpoint were 24.29 months.88 patient did not present any symptom and TFT abnormality.7 patient developed to papillary thyroid cancer and required thyroidectomy and hormone replacement.The risk factors to develp of hypothyroidism are initial TSH, TPOAb positivity. Conclusions: The Patients who had been diagnosed with thyroiditis on thyroid nodule should be followed up with regular TFT even though the TFT was normal at diagnosis.