Patients with primary hyperparathyroidism have a parathyroid adenoma approximately 80% of the time. Preoperative localization of parathyroid adenomas has been significantly improved by the utilization of high resolution (high frequency) real-time ultrasound. This technique was accurate in 14 (78%) of the 18 cases in our series. There were four false negatives and no false positives. This imaging technique can routinely identify lesions less than 1 cm. High resolution real-time ultrasound is fast, safe, and cost effective. It is an ideal screening test for the preoperative localization of parathyroid adenomas.