Ultrasound is very sensitive in evaluating the size of the thyroid gland and the presence of nodules within it. There are no specific signs indicative of malignancy though the majority of the differentiated carcinomas and all anaplastic tumors present as a hypoechoic mass. Since autonomous and ‘cold’ adenomas may show a similar echo pattern, a scintigraphic study is mandatory as part of the basic examination, except for euthyroid subjects without any nodularity on the ultrasound scans. Scintigraphically cold, echo-poor solid lesions require additional diagnostic procedures like aspiration cytology or biopsy until malignancy is definitely excluded. Monitoring of the thyroid volume during suppressive hormonal therapy is highly valuable for the early detection of’non-responders’ who probably will benefit from another man