Pathologic studies of thyroid nodules indicate that a definite percentage of nodular goiters are malignant, and that an even higher percentage are true neoplasms. Malignant tumors may arise from adenomas, involutionary nodules or possibly from nodules of the unclassified type. Some carcinomas of the thyroid gland are undoubtedly malignant processes from the start. Because of the high incidence of neoplasms, benign and malignant, in a group of single nodules of the thyroid gland, the presence of such nodules should warrant radical resections of the involved lobe and adjacent isthmus. The high incidence of epithelial growth activity in nodular involutionary goiters may revise the accepted practice of removing non-toxic nodular goiters only when clinical evidence of growth or local pressure is present.