Sudden death from hyperparathyroidism is not common. It can be prevented. Just as thyroid storm is a fulminating increase in the manifestations of hyperthyroidism, the majority of instances of parathyroid crisis occur as acute exacerbations of chronic hyperparathyroidism. Two major factors have been suggested which precipitate a crisis: high calcium intake, as in an ulcer regimen where antacids containing absorbable calcium are used, and immobilization, which increases the rate of skeletal demineralization.1 The end-result is an abnormal increase in serum and urinary calcium and phosphorus, followed by a rapid death. The mechanism of death presumably is cardiac poisoning by calcium with cardiac arrest in systole. This disease is often misdiagnosed or overlooked completely, yet it can be diagnosed rather easily and a cure almost assured. A thorough understanding of parathyroid crisis is necessary, therefore, if this disease is to be recognized and treated in time. Report of a Case