A series of 348 patients undergoing operative intervention because of thyroid masses is reviewed. The incidence of primary malignancy among these patients is 16.4%. Male sex and the presence of cervical adenopathy significantly increase the probability of malignancy. The presence of multiple nodules or a functional nodule on radioiodine thyroid scan significantly reduces the probability of cancer. A rational approach to thyroid nodules is presented based on these findings and new modalities that have become available.