Thyroid nodules are common entities, clinically important primarily because of their malignant potential. Serum thyrotropin and thyroid ultrasonography are pivotal in evaluating thyroid nodules. Fine-needle aspiration biopsy is the most accurate tool for diagnosing malignancy and selecting candidates for surgery. An approach to the initial evaluation and management of single nodules, functioning nodules, multinodular glands, incidental nodules, and cysts is discussed, as are therapeutic interventions for benign nodules. Thyroid cancer discovered during pregnancy is also discussed.