The diagnosis of incidental thyroid carcinoma in patients submitted to thyroidectomy for a benign disease is quite frequent. A retrospective analysis was performed on 240 patients submitted to surgical intervention in order to establish the incidence of the carcinoma. Onehundred sixtyfive patients (68.75%) were affected by benign disease (132 multinodular goiter, 30 uninodular goiter, 2 Plummer and 1 Basedow) and 75 (31.25%) by carcinoma. In 30 of 165 patients (18.2 %), affected by benign disease, occurred a histological diagnosis of thyroid carcinoma, (18 papillary carcinoma, 6 follicular carcinoma, 5 papillary carcinoma follicular variant and 1 oncocityc carcinoma). In this study it’s considered incidental thyroid carcinoma the one occurred in patients who never underwent FNA and there were no suspicious features in all exams that may suggest the presence of carcinoma. Fifteen of the 30 incidental carcinoma (50%) were microcarcinomas; in the other 13, dimensions were more than 1 cm, but less than 2 cm in 9 cases. Two patients had a sincronous carcinoma. Actually, these patients are still in a follow up program and no recurrency of disease is occasionally observed. This study shows that the only way to put doubts on the real benignity of the disease is the fine needle aspiration; there are no other instruments that could let think about the occurrence of the carcinoma. Moreover in the majority of cases the incidental carcinoma is a microcarcinoma, it doesn’t reach significant volume, may be not centered by a FNAB, but in must cases it’s not really biologically aggressive.