3,4-Methylenedioxymethamphetamine (MDMA, 'ecstasy') is an amphetamine synthetic analog widely used as an recreational drug. Acute and severe toxic effects following MDMA ingestion include hyperthermia, arrhythmias, rhabdomyolisis, disseminated intravascular coagulation, hepatotoxicity and even death. Recently, we treated a patient in whom hyperkalemia, in the absence of renal failure, aggravated the expected toxic complications of MDMA, becoming the immediate cause of his death.