Primary hyperparathyroidism is a rare disease that can be accurately diagnosed and effectively treated in most patients. The diagnosis is established by a persistent elevation of serum calcium and parathyroid hormone and by clinical evaluation. With the introduction of a biochemical screening test for calcium and the development of radiologic techniques, the detection of hyperparathyroidism has increased slightly. However, the parathyroidectomy is still not a common operation in Korea.Twenty-eight patients with primary hyperparathyroidism comprised of 14 males and 14 females, were treated by operation from January 1986 to December 1995 at Kyunghee University Hospital and the data were analyzed retrospectively. The results are as follows: 1) The sex distribution was 14 males & 14 females, and the age distribution was from 14 to 79 years. 2) The clincal manifestations were renal symptoms (42.9%), skeletal symptoms (28.6%), a neck mass (10.7%), pancreatitis (7.1%), no symptoms (7.1%), polydipsia (3.6%) in order of frequency. 3) Most of the patients showed hypercalcemia above 11mg/dl, but five patients had calcium levels which were either slightly increased or in the upper normal range . 4) The preoperative localization methods were mainly combinations of sonography, C.T.,and Tl-Tc subtraction scans and showed high sensitivity & specificity (above 90%). 5) The main tumor locations were the Rt. lower pole in 10 cases, the Rt. upper pole in 5 cases, the Lt. upper pole in 3 cases, the Lt. lower pole in 7 cases; there were 2 cases of ectopic location and 1case of hyperplasia at the Rt. upper & the Lt. lower pole. 6) The pathologic findings revealed a solitary adenoma in 25 patients, a carcinoma in two patients, and hyperplasia associated with MEN2a in 1 patient. 7) We experienced one case of recurrence after primary excision at the Rt. lower pole. Reoperation for a missed gland, after the primary operation, was performed in one patient; the excision of the tumor was performed successsfully. 8) We performed surgical excisions and 17 patients showed hypocalcemia postoperatively. Most of the hypocalcemia was transient and disappeared after ingestion of oral calcium agents or usuage of Vit. D3.