High-resolution ultrasound of the thyroid has optimal ability to image thyroid detail and is replacing scintigraphy as the initial method of choice for evaluating the thyroid. The thyroid ultrasound is now used not only for volume determination and detection of thyroid nodules but also for characterization of nodules as benign, malignant, or dubious, being able to predict cancer with 75% accuracy when using at least three ultrasound signs of malignancy, with a true negative of 97.8%. Another major indication is for monitoring the therapeutic response of thyroid nodules when TSH suppression is induced. Ultrasound provides needle guidance for biopsies of suspicious nodules and post-surgical follow-up of patients who have previously undergone surgery for thyroid cancer.