I retrospectively describe 20 episodes of water intoxication in 19 infants, with hypothermia, seizures, and hyponatremia. Overdilution of formula or aggressive supplementation with water or clear juices were documented in 16 of the 20 episodes. Seizures and respiratory distress were severe enough in six cases to require intubation and ventilatory support. Marked diaphoresis was noted as a premonitory symptom to seizures in eight children. The children were an average of 5.1 +/- 4.3 months of age; serum sodium values averaged 118 +/- 4.3 mmol/L. No evidence of excess production of antidiuretic hormone was found. Water intoxication in infants is common, and I discuss its possible relationship to demyelinating disease of the central nervous system.