High-resolution ultrasonography is the preferred method for evaluating thyroid nodules. Ultrasound of the thyroid gland should be performed for any “thyroid nodule” suspected on palpation or suggested by x-ray, CT or MRI. Ultrasound can confirm the presence of a “thyroid nodule” and determine the size, number, texture (cystic or solid), shape, border, envelope, calcification, blood supply, and relationship to surrounding tissue, as well as evaluate the lymph nodes in the neck. Certain ultrasound signs can help in the differentiation of benign and malignant thyroid nodules. Almost all nodules with the following two types of ultrasound changes are benign: 1) purely cystic nodules; 2) nodules with multiple small vesicles occupying more than 50% of the nodule volume with spongy changes; however, the following ultrasound signs suggest a high probability of thyroid cancer: 1) solid hypoechoic nodules; 2) nodules with abundant blood flow (normal thyroid hormones on thyroid function tests); 3) nodules with irregular shape and margins, and 4. Microcalcifications, pinpoint calcifications or clusters of calcifications within the node boundaries; 5. Abnormal ultrasound images of lymph nodes in the neck, such as round lymph nodes with irregular or blurred borders, uneven echogenicity within the lymph nodes, calcifications within the lymph nodes, poorly demarcated lymph node skin medulla, disappearance of lymphatic portals, and cystic changes of lymph nodes.