During a four-year period, 27 patients underwent total parathyroidectomy with autotransplantation of parathyroid tissue to the forearm. In order to minimize the risk of persistent or recurrent hyperparathyroidism (HPT), a routine thymic resection and a wide excision of fat tissue around the parathyroids was performed to ensure excision of possible supernumerary glands or rudimentary parathyroid tissue. The indications for operation were HPT secondary to chronic renal failure in 24 patients (22 of whom had hypercalcaemia) and persistent or recurrent primary HPT in 2 cases. One further patient, who had a multiple endocrine neoplasia syndrome type I, underwent this procedure at the primary parathyroid operation. Preoperative hypercalcaemia was reversed in all patients but three during the first postoperative days, concomitantly with a fall in the parathyroid hormone (PTH) level. Fourteen patients showed marked hypocalcaemia postoperatively, necessitating calcium or vitamin D supplementation. This medication could later be discontinued in all of them. Thirteen patients, including two of those with primary HPT, never required any supplemental therapy. Survival of the grafts was documented by several observations. In all patients normal serum calcium values were being maintained without supplemental therapy at follow-up. During induced hypocalcaemia a PTH secretory response was demonstrated in all eight studied patients with a gradient between the grafted and non-grafted arm. In two patients in whom the grafts were examined histologically 19 and 28 months after the transplantation, viable parathyroid tissue was observed. In the initial part of the study excised tissue was cryopreserved. Since persistent hypocalcaemia did not occur in our patients, we have now abandoned this safety precaution. Thus, total parathyroidectomy with autotransplantation of parathyroid tissue is a valuable method for restoring long-term parathyroid function in patients with secondary HPT and uraemia. It also appears of value in selected cases of primary HPT.