The thyroid nodule is a very common thyroid disease in adults, with an increasing incidence. Cancers are found in 10~14% of patients presenting with palpable thyroid nodules. As FNA is the single best test for evaluation of thyroid nodules, FNA should be the first test in patients with a thyroid nodule 1??or larger. According to the FNA findings, thyroid nodules are usually classified into three categories: malignant, benign, and suspicious/indeterminate lesions. Malignant nodules should be treated by surgery, while benign nodules can be followed without any medical treatment or suppressed by L-T4 treatment. Patients with suspicious/indeterminate nodules, are malignant in 10% to 20% of cases, should be advised to undergo surgery.