Poisoning is an uncommon manifestation of child abuse. The intentional administration of water to a child as a form of punishment has rarely been reported as the responsible substance among children who have been poisoned. We describe a case of a 5-year-old girl presenting with severe hyponatremia due to acute water intoxication. The patient was brought to the emergency room in status epilepticus. A history was obtained from the child's mother stating that the patient had been playing outside when she collapsed. She had had no known prior illnesses. Laboratory evaluation included a hemoglobin of 10.1 mg%, glucose of 60 mg%, serum sodium of 107 mEq/l, potassium of 3.2 mEq/l and chloride of 71 mEq/l. A CAT scan obtained approximately 1 h after admission revealed generalized cerebral edema. Careful examination of the skin revealed multiple linear ecchymosis of varying ages on the back and thighs and a hand print on the right flank. In addition, the child demonstrated severe failure to thrive with height, weight and bone age compatible with a 2.5-year-old girl. Appropriate therapy for severe hyponatremia was successfully instituted. For the next 12 h she was deeply somnolent, but the following morning was alert and conversant. She stated that she "would be good if she didn't have to drink any more water". The child's mother subsequently admitted that she frequently used water ingestion as a form of punishment. The child stabilized metabolically and demonstrated rapid in-hospital weight gain. She was placed in foster care at discharge and has had no further hyponatremia or seizures.(ABSTRACT TRUNCATED AT 250 WORDS)