The success of parathyroid surgery is determined by the identification and removal of all parathyroid tumors. Parathyroid tumors accumulate and retain 2-methoxyisobutylisonitrile (MIBI) labeled with technetium-99m. Intravenous injection of this radiopharmacon prior to parathyroid surgery allows identification of parathyroid tumors with a hand-held gamma detector. To assess the value of this technique, a case-control study was performed with 62 patient having nuclear-guided parathyroidectomy and 60 patients having conventional parathyroid explorations. The sensitivity rates of the MIBI probe in single and multiple gland disease were 84.6% and 63.0%, respectively. Rates of success, temporary and permanent hypoparathyroidism, and injury of the recurrent laryngeal nerve were similar in patients who underwent probe-guided surgery and those who had conventional surgery. In conclusion, although the MIBI probe appears to be a valuable tool in parathyroid surgery, its use has not improved the outcome of such surgery at our institution.