Sixteen cases of anaplasic thyroid carcinoma have been reviewed. In 13 cases out of 16, a diffuse invasion of one or both thyroid lobes and of the isthm associated with calcifications (50%) and necrosis (62%) was present. In 6 cases out of 8, CT Scan with contrast media injection has detected an extension into surrounding tissues. Twelve of the 16 patients presented cervical lymph nodes on the ultrasound examination and 4 of 8 patients presented mediastinal lymph nodes on the CT Scan. In 3 cases out of 16, the anaplasic carcinoma of the thyroid presented as a localized, hypoechoic nodule associated with a cervical lymph node in 1 case.