In the adult population, thyroid nodules are common and are increasingly detected by ultrasound examination or other scanning techniques. Depending on their size and ultrasonographic features, these nodules may require further investigation, including tissue diagnosis. Fine-needle aspiration (FNA) has become the predominant method to obtain tissue for microscopic analysis. In October 2007, the National Cancer Institute sponsored a conference to review the state of the science for the use of FNA in the management of thyroid nodules. This conference reviewed indications for thyroid FNA and pre-FNA requirements, training and credentialing, techniques for thyroid FNA, diagnostic terminology and morphologic criteria, utilization of ancillary studies, and post-FNA testing and treatment options. The results of those discussions have been published in both print and electronic versions. The aim of the current article was to discuss indications for FNA, diagnostic terminology, and post-FNA options, issues that are important to physicians who are managing patients with thyroid nodules. CA Cancer J Clin 2009;59:99–110. © 2009 American Cancer Society, Inc.