Ultrasound plays a prominent role in the management of thyroid disease and parathyroid adenomas. It can detect clinically impalpable thyroid nodules and characterize them as cystic, solid, or complex. Determining that a nodule is definitively benign or malignant is difficult, and so when indicated an ultrasound-guided fine-needle aspiration can be performed. In the follow-up of patients with thyroid cancer, ultrasound can be used alone or in conjunction with computed tomography (CT)/magnetic resonance imaging (MRI) to detect recurrent disease. Recurrences can be confirmed using ultrasound to guide fine-needle aspirations. To locate parathyroid adenomas, ultrasound is often used in conjunction with sestamibi scanning. If both studies agree on the location of the adenoma, the surgeon can perform focused surgery for its removal. In patients in whom the studies do not agree or in whom they do not detect the adenoma, further evaluation with CT or more preferably MRI is indicated.