We present a case of acute, symptomatic hyponatremia in a young woman that developed after use of 3,4-methylenedioxymethylamphetamine (MDMA), more commonly known as "ecstasy." The patient was treated with 5% saline and had complete recovery. The pathogenesis of MDMA-associated hyponatremia involves excessive water intake and inappropriately elevated antidiuretic hormone (ADH) levels. It seems...