The traditional surgical approach for the treatment of primary hyperparathyroidism (HPT) has been routine bilateral surgical exploration. Our aim was to evaluate pre-operative ultrasonography (U/S) in altering our practice to selective unilateral neck exploration.A retrospective study was conducted involving 53 patients who had parathyroidectomy over a 5-year period (1989-1994), 41 of whom with the diagnosis of HPT had pre-operative neck U/S.Thirty-eight patients had a single adenoma, one had parathyroid cancer, and two had multiple adenomas. Thirty-six of 41 (88%) patients were true positives, two (5%) false positives, two (5%) false negatives and one (2%) was true negative. Based on the surgeon's personal preference and U/S results, 21/41 (51%) of patients had bilateral and 20/41 (49%) had unilateral neck exploration. All the 41 patients had resolution of the hypercalcemia postoperatively. Eighteen of 38 (47%) patients with a single adenoma had bilateral neck exploration and only in two patients was this necessary.Patients undergoing parathyroid surgery for HPT should have preoperative U/S and, if a single enlarged parathyroid gland is found, unilateral U/S guided neck exploration is safe and economical. In all the other patients, bilateral exploration is the preferred approach.