Parathyroid function, defined as the ability to maintain normocalcemia without substitution, was evaluated in 36 patients following total thyroidectomy for carcinoma. In 16 patients, all visualized parathyroid tissue was sliced and autotransplanted into muscle pockets; one year after the operation, 11 patients had substitution for lack of parathyroid function. In 20 patients, the parathyroid glands were preserved in situ with intact vascular supply; one year postoperatively, three patients had evidence of persistent hypoparathyroidism. The difference in the parathyroid insufficiency rate is significant, p less than 0.005. We conclude that parathyroid autotransplantation has been a failure io preserve the parathyroids in situ whenever this is feasible, autotransplantation being reserved for parathyroids unfortunately removed or devascularized.