Thyroid primary cancer involves 1.5% of malignant tumors and it causes yearly 0.5% cancer mortality. It is usually related to eu- or hypothyroidism, whereas it is rarely associated with hyperthyroidism. The Authors deal with controversial issues concerning thyroid oncogenesis and surgical strategies. However, they have not ignored epidemiological data and clinical features most peculiar to various neoplastic histotypes. They also report on their own experience with 156 cases of thyroid CA, out of 2.510 surgically treated thyroid diseases, which were being investigated from 1969 to 1998. The Authors recognize that an appropriate approach to thyroid neoplastic diseases arises from a careful evaluation of all parameters (T, N, M, histotype, patient's, age, intraoperative assessment etc.) characterizing their polymorphism.