Palpable thyroid nodules occur in 4 to 7 percent of the population, but nodules found incidentally on ultrasonography suggest a prevalence of 19 to 67 percent. The majority of thyroid nodules are asymptomatic. Because about 5 percent of all palpable nodules are found to be malignant, the main objective of evaluating thyroid nodules is to exclude malignancy. Laboratory evaluation, including a thyroid-stimulating hormone test, can help differentiate a thyrotoxic nodule from an euthyroid nodule. In euthyroid patients with a nodule, fine-needle aspiration should be performed, and radionuclide scanning should be reserved for patients with indeterminate cytology or thyrotoxicosis. Insufficient specimens from fine-needle aspiration decrease when ultrasound guidance is used. Surgery is the primary treatment for malignant lesions, and the extent of surgery depends on the extent and type of disease. Ablation by postoperative radioactive iodine is done for high-risk patients--identified as those with metastatic or residual disease. While suppressive therapy with thyroxine is frequently used postoperatively for malignant lesions, its use for management of benign solitary thyroid nodules remains controversial.