Malignant hyperpyrexia is a genetically related syndrome that cannot be predicted reliably in advance of administration of anesthesia except by a strong family history. The definitive etiology is unknown, although triggering agents that release calcium from the calcium-storing sarcoplasmic membrane of the muscle cell are highly suspect. As soon as the syndrome is diagnosed, therapy must be prompt, vigorous, and carried out with the same urgency as a cardiac arrest. Specific therapy with dantrolene sodium may prove to be an answer to this serious problem in anesthetic practice.