In a 5-year prospective study in an endemic area for goiter, 275 patients with solitary thyroid nodules or with predominant nodules in multinodular goiters underwent surgery without selection on clinical grounds. The incidence of cancer was 13.1%. Preoperative diagnosis was based on personal history, local signs and radioisotope data. As compared with histologic findings, clinical and scanning data yielded a diagnostic accuracy of 19% and 31% respectively. 30% of all malignancies were not suspected preoperatively. 100% identification of cancer is possible only it all nodules are excised. Selection is, however, necessary: our data suggested that patients under 20 and over 50 years, all males, and goiters with more than 2 physical and/or scanning signs suspect for cancer should be operated upon. Much unnecessary surgery would be save and most, but not all, cancers would be excised.