A 12-year-old boy with tuberculous meningitis and hydrocephalous, after undergoing revision of ventriculo-peritoneal shunt had persistent impairment of sensorium and episodes of hyponatremia (serum sodium 104 to 125 mmol/l), accompanied by polyuria, signs of poor peripheral, perfusion hypotension and low CVP, and high urinary sodium excretion (114-60 mmol/l). A diagnosis of cerebral salt wasting syndrome (CSWS) was made and was treated with saline replacement and fludrocortisone (10 microg/kg/day). Within next 3 days the sensorium, signs of shock, urine output and serum and urinary sodium returned to normal. The case illustrates that life-threatening hyponatremia in a child with neurological illness could be caused by CSWS, which must be differentiated from Syndrome of inappropriate antidiuretic hormone secretion (SIADH), as CSWS requires rigorous salt and volume replacement in contrast to fluid restriction in SIADH.