MDMA (3,4-methylenedioxymethamphetamine), popularly known as “Ecstasy,” was first introduced and patented by Merck & Co., Inc., in 1914 as an appetite suppressant. Currently, its primary role is as an illegal stimulant used to produce a euphoric effect during parties. This case report de scribes a 31-year-old man who, after taking 3 tablets of Ecstasy, presented to an emergency department with a decreased level of consciousness and became progressively hyperthermic and rigid. During the course of his acute illness, his temperature reached 42.2°C rectally. He was given mechanical ventilation. He was aggressively cooled and dantrolene was initiated. Soon after the administration of dantrolene his temperature decreased and his rigidity began to resolve. The only complication was rhabdomyolysis with a creatine kinase level increasing to over 150 μkat/L. This did not progress to acute renal failure. The patient made a full recovery and was discharged to psychiatry for assessment.