A retrospective review of 54 cases of primary hyperparathyroidism operated upon by five general surgeons at Santa Barbara Cottage Hospital between March 1998 and March 2001 was performed to determine whether positive preoperative sestamibi localization (PSL) of a solitary adenoma combined with intraoperative parathyroid hormone assay (IOPHA) could predict successful focused unilateral neck exploration. A solitary adenoma was found in each of 50 patients (93%). PSL for solitary adenomas had an accuracy of 87 per cent, positive predictive value (PPV) of 96 per cent, sensitivity of 90 per cent, and specificity of 50 per cent. Forty-five patients (83%) achieved a 50 per cent reduction in IOPHA at 10 minutes after excision of a solitary adenoma for an accuracy of 85 per cent, PPV of 97 per cent, sensitivity of 88 per cent, and specificity of 50 per cent. All patients remain eucalcemic. The combination of PSL and IOPHA resulted in a PPV of 97.5 per cent and a sensitivity of 100 per cent. From these data we conclude that a focused unilateral neck exploration could have been performed successfully in 78 per cent of the cases.