Parathyroid glands are small endocrine glands that secrete a hormone which controls blood calcium levels. Primary hyperparathyroidism (PH) is a common disorder whereby one or more of these glands may enlarge and overproduce their hormone. Subsequently, the elevated blood calcium can cause many other symptoms and problems. The standard treatment is surgical removal of the gland(s) causing the disorder. The standard safe and effective operation has been the bilateral open parathyroid exploration (BOPE). A newer procedure using a radioactive compound that concentrates in the parathyroid glands allows a more limited operation to find and remove the causative gland [Minimally-Invasive Radioguided Parathyroidectomy (MIRP)]. The radiation exposure is minimal and safe. Although the operation may prove to be less expensive, it is not certain whether it is as effective or as safe as BOPE. This study serves to directly compare the costs, the effectiveness, and the safety associated with each type of operation. All patients (adolescents and older) with PH are candidates to participate. The participants will be randomly assigned to the MIRP group or the BOPE group independently of patient or physician preferences. MIRP patients will undergo a sestamibi nuclear medicine scan to attempt to localize the specific parathyroid gland causing the hyperparathyroidism and subsequently a limited operation under local anesthesia to remove the single gland. Parathyroid hormone levels will be measured during the operation to ensure that the patient has been cured. If not, the standard BOPE procedure will be completed. The total cost of the care will be tracked for each group. Careful testing for complications such as vocal cord dysfunction will be done. General Health status and pain levels will be measured before and after each operation. Patient satisfaction with the operation and care will also be assessed.