Postoperative parathyroid function was evaluated in 24 total thyroidectomy and 8 subtotal thyroidectomy patients seen by our department between January 1995 and July 1997. Parathyroid function was assessed by measuring the level of serum intact parathyroid hormon (intact-PTH). Hypoparathyroidism was avoided in 23 patients (95.8%) who received a total thyroidectomy and in 7 patients (87.5%) who received a subtotal thyroidectomy. Supplementary therapy for hypoparathyroidism was not required as long as the blood supply to more than two parathyroid glands was preserved. Half of the patients in this study did not require any postoperative supplementary therapy. Thus, the preservation of more than two parathyroid glands is essential for the prevention of hypoparathyroidism. In cases where the parathyroid glands had been resected, parathyroid gland transplantation were performed. In all cases, supplementary therapy was eventually no longer required. In two cases requiring supplementary therapy, a normal range of parathyroid activity was observed 30 months after surgery. The administration of vitamin D3 may suppress the recovery of parathyroid function in patients recieving parathyroid transplantations.