The authors report their experience with 453 cases of thyroid nodules observed over a period of 5 years. The intention was to determine the incidence of malignant lesions. A female prevalence of the nodular pathology was clearly evident (7.2%), with a maximum incidence between the 3rd and 6th decade. Among malignant tumors (14.2%) the following histologic types were most frequently found: papillary adenocarcinoma (5.7%), follicular adenocarcinoma (2.7%), occult cancer (2.7%), anaplastic cancer (2.3%). Up to the 4th decade female prevalence was clearly evident (Max in the 3rd decade; F/M ratio = 6.5); then an increased male incidence was registered bringing to a reduction of the F/M ratio (1.5 in the 5th and 6th decade) and to its inversion in the 7th decade (M/F = 1.25).