Background: Minimally invasive parathyroidectomy for primary hyperparathyroidism depends on accurate preoperative imaging, which is traditionally accomplished by 99mTc-sestamibi scanning. Cervical ultrasound is gaining in use, but it is unclear how much information it adds to the routine use of 99mTc-sestamibi scans. Methods: A prospectively maintained database of patients undergoing parathyroidectomy for primary hyperparathyroidism was queried, and the utility of cervical ultrasound in preoperative planning was analyzed. Results: Between July 2002 and November 2009, 310 patients with primary hyperparathyroidism underwent both 99mTc-sestamibi and ultrasound imaging. Ultrasound added new information to 99mTc-sestamibi in 43 patients (14%) by finding either the correct enlarged gland (n = 40, 88%) or additional enlarged glands (n = 5, 12%). Ultrasound correctly localized glands in 38 of 85 (45%) patients with a negative 99mTc-sestamibi, allowing for a minimally invasive parathyroidectomy in those patients. However, in the 206 patients (66%) who had a 1-gland positive 99mTc-sestamibi, ultrasound only added information for 8 patients (4%). When compared with radiology-performed ultrasound, surgeon-performed ultrasound was successful in localizing additional glands in 27 (15%) versus 17 patients (10%) (P < 0.001). Conclusions: Ultrasound led to additional localization information in 14% of patients, although this benefit was less in patients with a clearly positive 1-gland 99mTc-sestamibi scan. Cervical ultrasound provides added benefit to 99mTc-sestamibi scanning in patients with primary hyperparathyroidism, but its greatest utility is when performed by a surgeon in patients with a negative 99mTc- sestamibi scan. © 2011 Society of Surgical Oncology.