Parathyroid surgery has an excellent rate of success, particularly in high-volume centers. Despite this, surgical failures do occur, and the most common cause is a missed single adenoma. While ectopic parathyroid adenomas do occur, these are uncommon, and most “missed” parathyroid adenomas are in eutopic locations or immediately adjacent. Overly descended inferior (thymus) and superior (deep prevertebral musculature) parathyroid glands are some of the most commonly missed glands. The parathyroid glands have a consistent relationship with the recurrent laryngeal nerve with superior glands positioned dorsal to the nerve. This information can be leveraged to narrow the area of search for a “missing” gland. This chapter discusses the anatomy of the parathyroid glands in detail and outlines a practical approach to identification of a “missing” parathyroid gland intraoperatively.