Anaplastic carcinoma of the thyroid gland is a tumor of great malignant potential. The majority of the patients die in the period of 6-24 months after diagnosis is made. A review of 90 cases of anaplastic carcinoma of the thyroid gland surgically treated in the Department for Endocrine Surgery of The Second Surgical Clinic and Center for Endocrine Surgery of the Clinical Centre of Serbia revealed that anaplastic carcinomas were 11.3% of all the thyroid carcinomas (796) diagnosed in the cited period. The patient's age varied from 40 to 80 (mean 63.7 years). The incidence in women is twice as large as in men (2.1:1). Intraoperative histopathologic diagnosis was made in all the patients. The variations in histological structure were noticed. Dominant histopathologic features included pleomorphic giant and spindle cells, with irregular hyperchromatic nuclei and many aberrant mitotic figures with necrosis and infiltration of blood vessels by neoplastic tissue in most of the cases.