The Authors evaluated the results obtained in 145 patients operated on for hyperparathyroidism: 109 patients had primary hyperparathyroidism and 36 patients had secondary hyperparathyroidism. Preoperative localization by ultrasonography was assured in all cases, while only few patients were preoperatively evaluated by arteriography and selected venous sampling of the parathyroid hormone concentration. After surgical resection for primary hyperparathyroidism, transient postoperative hypoparathyroidism occurred in 30 patients (27.5%), recurrent disease occurred in 3 patients (2.7%), while 1 patient experienced persistent hypoparathyroidism (1%). In 3 patients (3%), resection of a solitary adenoma and biopsy of all parathyroid glands resulted in a permanent hypoparathyroidism which required long-term administration of vitamin D and oral calcium. Neither recurrent nor persistent hyperparathyroidism occurred in patients surgically treated for secondary hyperparathyroidism, and no postoperative hypoparathyroidism was registered. The Authors emphasize the importance of an adequate surgical strategy and accurate initial cervical exploration of the parathyroid glands as a necessary step for the correct treatment of this challenging disease.