To evaluate the utility of clinical features for the selection of patients with thyroid lesions suitable for diagnosis by fine-needle aspiration cytologic study, we reviewed 149 cases with complete clinical histories, laboratory evaluations, fine-needle aspirates, and histologic study of the index lesion. Review of these data demonstrated that only the presence of lymphadenopathy was of statistical value in the distinction of benign from malignant nodules. Moreover, once an aspiration diagnosis of "follicular neoplasm" had been made, no clinical, radiologic, or laboratory test aided in the distinction of follicular adenoma from follicular carcinoma.