Parathyroid storm in patients with primary hyperparathyroidism has previously been described as hyperparathyroid crisis, parathyroid intoxication or acute hyperparathyroidism. Whatever the nomenclature, all emphasize the severity and urgency of this disease entity. Although fewer than 200 cases have been described since the first report by Dawson in 1932, it is generally agreed that parathyroid storm is more prevalent than commonly appreciated. The symptoms and signs of the syndrome are not only due to the hypercalcemia, but also to the toxic effects of the parathyroid hormone (PTH). Its wide, but nonspecific clinical presentations make it easily confused with other cardiovascular or renal diseases. The mortality rate in untreated cases of parathyroid storm is essentially 100%. With combined medical-surgical treatment, it is still reported to be as high as 40%. Two patients with parathyroid storm were encountered at our institute recently, they both presented with severe hypercalcemia, consciousness disturbance and acute renal failure. The serum level of the intact form of PTH (iPTH) in both patients was greater than 1,000 pg/mL. Case 1, a 63-year-old female, presented with hypercalcemic crisis. Initially, good responsiveness to a saline infusion, steroids and furosemide administration was noted. Unfortunately, she became comatous after fine-needle aspiration of the parathyroid tumor. The recurrent storm was refractory to medical therapy, but was treated successfully by surgical removal of the single adenoma. This is a rare reported case regarding a hyperparathyroid storm after fine-needle aspiration of a parathyroid adenoma.(ABSTRACT TRUNCATED AT 250 WORDS)