Exploration of the neck for primary hyperparathyroidism is facilitated if the parathyroid glands can be localized preoperatively. Magnetic resonance imaging is a noninvasive and relatively safe procedure that is capable of distinguishing and differentiating small soft-tissue structures. Ten patients with primary hyperparathyroidism underwent preoperative diagnostic magnetic resonance imaging followed by cervical exploration. In 9 of these patients (90 percent), imaging correctly predicted the location of a single enlarged parathyroid gland, and in one patient the findings were misleading. All 10 patients proved to have single adenomas in orthotopic locations. Based on this early experience, magnetic resonance imaging appears to be a promising technique for preoperative localization of an enlarged parathyroid gland.