Primary hyperparathyroidism is characterized by hypercalcemia with loss of bone mass. After parathyroidectomy, hypocalcemia may develop in some patients due to unregulated bone mineralization. Preoperative administration of bisphosphonates, potent inhibitors of osteoclast activity, may prevent postoperative hypocalcemia after parathyroidectomy. We retrospectively reviewed medical records to investigate the effect of bisphosphonate pretreatment on serum calcium level changes after parathyroidectomy. Twenty-three patients with a diagnosis of primary hyperparathyroidism underwent parathyroidectomy between April 1997 and August 2002. Clinical and laboratory data were collected before and after the operation. These patients were divided into two groups; those showing hungry bone syndrome (n = 9) and those not (n = 14). None of the 9 patients with hungry bone syndrome had received bisphosphonate pretreatment. Of the 14 patients without hungry bone syndrome, 6 had received bisphosphonate pretreatment (P < 0.05). Furthermore, preoperative calcium concentration was not related to the occurrence of hypo-calcemia in those without bisphosphonate pretreatment. In conclusion, administration of bisphosphonates in primary hyperparathyroidism can prevent the occurrence of hungry bone syndrome after parathyroidectomy.