IN 1908, Kocher1 implanted autologous thyroid tissue, "the size of a pea," into the metaphysis of dogs. "A period of time later," he performed a total thyroparathyroidectomy. The animals did not develop tetany (the exact percentage of those benefited was not given). Kocher reported that he implanted only thyroid tissue, and postulated that "thyroid tissue gives rise to the development of parathyroid." During the last half-century, 100 patients with acute and chronic hypoparathyroidism have been "successfully" treated by homologous parathyroid, heterologous parathyroid, and nonspecific tissue implants. Critical appraisal of the reported successes indicates that 71 of the 100 experienced unquestionable symptomatic improvement for periods of at least 3 months. However, convincing histologic proof of surviving parathyroid tissue was not demonstrated in these cases.2 It is difficult to avoid reaching the conclusion that symptomatic benefit, secondary to parathyroid implantation, may result from adaptation to the hypoparathyroid state stimulated