Primary hyperparathyroidism is most frequently due to a single parathyroid adenoma and responds favorably to surgical resection. Rarely, the parathyroid glands may be found in ectopic locations, including the mediastinum. The traditional approach for resection of a mediastinal parathyroid adenoma is via a median sternotomy. We describe an alternative approach, using video-assisted thoracoscopic surgery (VATS). A 16 year old male presented to his pediatrician complaining of fatigue, musculoskeletal leg pain and weight loss of 10 lbs. He was found to have elevated calcium levels (total calcium 15.6 mg/dL, normal 8.5 ? 10.5 mg/dL). He was admitted and treated with hydration, loop diuretics, calcitonin and biphosphonates with good response. The intact parathyroid hormone (PTH) level was markedly elevated (iPTH 3690 pg/mL, normal 11-68 pg/mL). The rest of the endocrine evaluation was unremarkable. A Tc99m sestamibi scan showed increased activity in the right superior mediastinum. Other imaging studies (CT scan, MRI) suggested the possibility of a soft tissue mass in the same area. A right thoracoscopic exploration was performed; the ectopic adenoma was identified just anterior to the junction of the right atrium and the superior vena cava and removed. Itraoperative rapid PTH assay showed a marked decrease after the resection (911 to 318 pg/mL). Postoperatively, the calcium and PTH levels returned to normal. Pathological examination confirmed the presence of a parathyroid adenoma. Thoracoscopic resection of mediastinal parathyroid adenomas is feasible and avoids the need for median sternotomy. Preoperative localization and intraoperative PTH assays are important tools for identification of the adenoma and confirmation of adequate resection.