Acute hyperparathyroidism is a condition which has been known as acute parathyroid intoxication, parathyroid crisis, parathormone intoxication and calcium intoxication since 1926 when Collip injecting parathyroid hormone into dogs, observed vomiting, diarrhea and atony with an increase of serum calcium level to above 20 mg/dl. When considering the 727 cases of primary HPT operated in our surgical department since 1975 to December 2003, 47 had a calcium level higher than 14.5 mg.; 29 of them showed signs of hypercalcemic crisis. In this group of patients, males were more numerous than females (18 males, 11 females); the mean age was 54; mean PTH level and serum calcium were respectively 593.4 pg/ml and 17.1 mg/dl. A renal involvement was observed in 71.4% of the cases, skeletal in 48.5%, gastrointestinal in 2.8%, and nervous in 57.1%. A MEN syndrome was never seen. A single adenoma occurred in 68.7% of the cases; a double adenoma in 17.1%; a hyperplasia in 5.7%; a carcinoma in 8.5%. A cystic adenoma was observed in 5.7% of the cases. The mean weight of the removed glands was 4947 mg. A complete recovery was obtained in 94% of the cases. We will show in this video 2 of these cases which had particular features. The first a 79 year old female, who had a history of osteodistrophy and neurological symptoms. She was hospitalized because of a metabolic coma with calcium level at 22 mg and PTH higher than 2000 pg. A deep venous peripherical thrombosis and a pulmonary artery thrombosis were observed and a preoperative caval filter was positioned. The scintigraphy was positive showing a large parathyroid on the right side of the neck. A median cervicotomy was performed. Taking into consideration the scintigraphy, exploration started on the right side of the neck. There was a large mass situated close to the esophagus. Considering the possibility of a carcinoma, the superior thyroid pedicle was ligated and cut in order to perform a right lobectomy. The operation continued, cautiously isolating the parathyroid mass. The recurrent nerve was adherent to the parathyroid capsule. The right lobe was cautiously isolated following the recurrent nerve. Right total lobectomy was performed removing the superior parathyroid neoplasm and the inferior gland, situated on the inferior pole (it appeared normal). The PTH fell to 140 from 1240. The left side of the neck was explored and the superior parathyroid identified: it appeared to be enlarged. The inferior parathyroid was in the thyrothimic ligament and it appeared normal. The superior gland was then removed. The PTH fell to 40 pg. The second case was a 44 year old male, who had a long history of kidney stones. At the time of hospitalization calcium level was 18 mg/dl and PTH 250 pg/ml. He was seriously confused with nausea and vomiting. A pleural effusion was observed and a TC scan showed splenic and kidney infarcts. The scintigraphy showed two positive images on both sides of the neck. Minicervical incision was performed and the left superior parathyroid gland, weighing 1100 mg, was removed. The inferior parathyroid appeared normal. On the right side the superior and the inferior glands appeared to be normal. PTH fell more than 50% in 10 minutes. 1 month after the operation the 2 patients had completely recovered without any signs of vascular thrombosis.