Arrested descent of the inferior parathyroid gland (“parathymus”) during embryologic development may leave the gland stranded high in the neck. Adenomas of such undescended glands are a rare cause of primary hyperparathyroidism, but they may not be uncommon among patients who have already had a failed cervical exploration. Unless the surgeon is aware of this entity, he will probably overlook it. If one is to find these tumors, it is necessary to extend the dissection upward above the superior pole of the thyroid gland, sometimes as far as the angle of the jaw. Adenomas of undescended “parathymus” glands were encountered in seven patients during a recent 20 month (May 1975 through December 1976) surgical experience encompassing 414 primary operations and 27 reoperations for hyperparathyroidism. These tumors were found at initial exploration in one patient and at reoperation in six patients. The individual case histories are presented to illustrate the difficulties posed by this anatomic variant.