Results are reported of four and a half years of experience with autotransplantation and cryopreservation of parathyroid tissue in thyro-parathyroid surgery. One hundred patients with hyperparathyroidism secondary to renal insufficiency were treated by total parathyroidectomy and partial autotransplantation, immediate in 98 cases and secondarily using their frozen stored tissue in the other two cases. Results were compared with those in 13 other patients treated during the same period by subtotal parathyroidectomy. Seven of 46 patients with primary parathyroid hyperplasia underwent total parathyroidectomy with immediate partial autotransplantation. Grafts were not used in the other two previously cervicotomized patients. All parathyroid tissue removed during these operations was frozen and stored if not used for grafting. Of 116 patients treated by enlarged total thyroidectomy for cancer, 34 received parathyroid autotransplants; complementary in 19 cases and substitutive in 15. Technique and results are described, and respective indications for autotransplantation and parathyroid cryopreservation discussed with respect to primary, secondary, persisting or recurrent hyperparathyroidism, and to total thyroidectomy for cancer.