Parathyroid insufficiency is fortunately a comparatively rare complication following surgical treatment of the thyroid gland. Boothby1 stated that 88 patients with this condition were treated at the Mayo Clinic between 1924 and 1929. This included patients operated on elsewhere as well as persons from the group on whom 13,300 thyroidectomies were performed at the clinic during this period. Because of the possibility of its occurrence, however, every surgeon should be familiar with the treatment of the condition. MacCallum and Voegtlin in 1909 advanced the hypothesis that parathyroid tetany is due to a withdrawal of soluble and physiologically available calcium salts from the blood and especially from the nervous system. More recently McLean, Barnes and Hastings2 have shown that the parathyroid glands control the concentration of the calcium ions in the blood plasma. Various methods of treatment have been reported, the most common being the use of various calcium