We report the case of a 61-year-old woman who suffered a parathyroid crisis due to a parathyroid adenoma. The patient presented with the typical clinical symptoms of hypercalcemia. Ca(+2) and PTH were markedly increased. Initially, she was treated conservatively until Ca(+2) returned to normal levels. Then, she underwent surgical excision of a newly diagnosed parathyroid adenoma. Parathyroid crisis (PC), also known as parathyroid storm or acute primary hyperparathyroidism, is a rare and serious complication of primary hyperparathyroidism (PH). Fewer than 200 cases have been described in the literature. Prognosis is poor: mortality is 100% in non-operable cases and 20% in cases in which parathyroidectomy is performed. We emphasize the importance of early diagnosis and aggressive treatment.