Thirty patients were operated on during the past 15 years for primary hyperparathyroidism. In each case serum calcium and phosphate levels returned to normal following excision of a solitary parathyroid adenoma. In 27 patients the tumor was located in the cervical region while three were found in the mediastinum. A high prevalence of unsuspected thyroid neoplasm was seen including four cases of benign adenoma and three cases of follicular carcinoma.