A case of ecstasy-related hyponatremia occurred in a 19-year old woman that had consumed ethanol and one tablet of ecstasy approximately 12 hours before hospital admission. MDMA was detected in urine with GCMS, but concentration is not reported. On admission, the patient was incoherent and had blood sodium of 121 nmol/L and urine sodium of 111 nmol/L. CT scan showed signs of cerebral edema. The patient was treated with hypertonic saline and fluid restriction, and serum sodium recovered to 132 nmol/L within 24 hours. Full recovery was reported after 48 h. The report includes a discussion of putative causes of MDMA-associated hyponatremia and treatment strategies, and includes very specific formulae for correcting hyponatremia using hypertonic fluid. The author advises caution in using fluids to correct MDMA-associated hyponatremia, since it might have arisen from SIADH (syndrome of inappropriate release of antidiuretic hormone).