Although sestamibi scanning has been shown to have greater sensitivity and specificity than other preoperative localization techniques for parathyroid adenoma, it is unclear whether preoperative scanning improves outcomes for parathyroid surgery. Data from 528 consecutive patients who underwent neck exploration for primary hyperparathyroidism by one surgeon were collected prospectively over a 5-yr period. Patients were classified by preoperative scanning status (no scan, positive scan, and negative scan), and outcomes were compared in terms of operative time, length of hospital stay, and cure rate. Patients who had undergone a previous parathyroid operation and patients who received alternate preoperative localization techniques (ultrasound, magnetic resonance imaging, and computed tomography) were excluded from the study. All scans were ordered by the referring physician-the surgeon made no recommendations for preoperative scanning. All groups were similar in terms of gender, age, anesthesia class, body habitus, and complication rate. There was no significant difference in cure rate between patients who had preoperative scanning (97.5%) vs. those who did not (99.3%); however, there was a significant difference in cure rate between the negative-scan group (92.7%) and the positive and no-scan groups (99.3%, P < 0.01). In patients without concomitant thyroid surgery, there was no significant difference in operative time between the no scan (42.4 +/- 14.9 min) vs. the all-scan group (40.2 +/- 15.2 min); however, there was a significant difference between the negative scan group (44.5 +/- 21.9 min) and the positive scan group (38.5 +/- 12.6 min, P < 0.01). There was no significant difference in length of hospital stay among the three groups. These results suggest that, although preoperative sestamibi scanning does not alter the outcome of parathyroid surgery, it does identify those patients who are less likely to be cured.