Thyroid nodules are very common and there have been statistics that the incidence of nodules is about 60% in the 60 year old age group. The large number of thyroid checkups in recent years has led to the discovery of numerous thyroid nodules. When a nodule is found, the first step is for the ultrasonographer to determine the possibility of benignity or malignancy. If it is a typical benign nodule, such as a nodular goiter, Hashimoto’s node, or hyperplastic nodule, regular follow-up ultrasound is usually sufficient, about twice a year. If there is a risk of malignancy, ultrasound-guided puncture biopsy is recommended. If malignancy is suspected, nodules less than 5mm and no infiltration of surrounding tissues can be reviewed every 3 months and may not grow for months~years, but if there is an increase, puncture biopsy may be considered in the range of 5~10mm.