Surgery has been used to treat primary hyperparathyroidism since 1925. The indications for surgery in mild hypercalcaemia and in asymptomatic patients are not clearly established, but the attitude to surgery is liberal if the surgical results are good. The value of preoperative localisation studies prior to the initial neck exploration is also questionable. We evaluated the results of 147 consecutive patients, who had been operated on for hyperparathyroidism. We analysed also the results of preoperative localisation studies. Most of the patients had symptoms which could be related to primary hyperparathyroidism. Hypercalcaemia was cured by surgery in 96 % of the patients, but six patients needed more than one procedure. Permanent hypocalcaemia ensued in 3 % of the patients. Complications were rare, but occurred more often in patients with previous thyroid or parathyroid operations, and in patients who needed a simultaneous thyroid operation. Preoperative ultrasonography, which was made in 135 patients, revealed an abnormal parathyroid gland correctly in 47 % of the patients. The result was incorrect in 26 % and there was no finding in 27 % of the patients. Thallium-technetium subtraction scintigraphy, which was made in 96 patients, was correct in 29 incorrect 41 %, and uninformative in 30 % of the patients. Angiography was performed in eight patients with a correct finding in six patients. We conclude that operative treatment for primary hyperparathyroidism is successful and safe in experienced hands. The reliability of noninvasive localisation studies is poor, and they are not necessary before the initial neck explorations.