Objective To evaluate the diagnosis and differential diagnosis methods for chronic lymphocytic thyroiditis(CLT).Methods One hundred and eight patients with CLT were treated in our department during recent 20 years,the clinical data were analyzed retrospectively.The diagnostic methods included thyroid function measurement,anti-thyroid antibody measurement,image detection,fine needle aspiration,diagnostic drug therapy and biopsy exam during operation.The preoperative examinations and diagnoses of 94 patients,who had received operation,were compared with postoperative pathological results.Results Forteen of the 108 cases did not receive any operation,of whom,9 had a definite diagnosis of CLT by fine needle biopsy under color ultrasound and 5 by drug(prednisone) diagnostic treatment.Before operation,57 patients were diagnosed as nodular goiter,16 as thyroid cancer and 13 as nodular goiter associated with hyperthyroidism.Only 8 patents were diagnosed as CLT with nodular goiter.Postoperative pathological reports were simple CLT in 59 cases(62.7%),CLT with nodular goiter in 19(20.2%),CLT with hyperthyriodism in 10(10.6%)and CLT with thyroid cancer in 6(6.3%).The preoperative misdiagnosis rate reached 91.5%(86cases).Conclusions It is easy for CLT to be misdiagnosed because of the complex clinical manifestations.Careful analysis of examination results,especially thyroid function measurement,anti-thyroid antibody measurement and image detection is significant for confirming the diagnosis.The fine needle biopsy and diagnostic drug treatment are better methods for CLT diagnosis.Unwarranted operation should be avoided in patients with CLT.