Parathyroid carcinoma is a rare, reported to be less than 1% of patients with primary hyperparathyroidism. Recently, cell cycle regulators such as the retinoblastoma gene and p53 have been implicated in the pathogenesis of parathyroid carcinoma. Yet definite diagnosis remains difficult not only clinically but also pathologically. However, the clinical presentation, biochemical and hormonal findings, and appearance at the operation may possibly raise suspicion regarding the diagnosis. A radical en bloc resection at the primary operation is most important. Even after a successful initial operation parathyroid carcinoma carries an increased risk of recurrence. There is wide diversity in the interval between the initial operation and the manifestation of metastasis. Histopathology and DNA ploidy are valuable predictors of the clinical outcome. Because the severe hypercalcemia it engenders has catastrophic consequences, proper management of the recurrent hypercalcemia is also mandatory. The lung is the most common site of distant metastasis. Selected patients with pulmonary metastasis of parathyroid carcinoma can obtain significant benefit from aggressive surgical resection even when they have multiple or recurrent lesions. When hypercalcemia is refractory to surgical resection, medical treatment with bisphosphonate has a beneficial effect. Semin.