We describe a five-week-old boy who had seizures and extreme hypernatraemia secondary to ingesting an improper home-made formula. Initial sodium concentration was 211 mmol.l-1. Other clinical and biological features were moderate dehydration and renal insufficiency with generous urine output and high urinary sodium concentration. Fluid therapy with hypotonic dextrose solution corrected the volume deficit in 48 h and progressively decreased the serum sodium concentration. During ICU stay the patient developed recurrent episodes of seizures and pulmonary oedema requiring mechanical ventilation for five days. Recovery was complete with no abnormal sequelae after a ten-month follow-up. Salt poisoning is in unusual cause of extreme hypernatraemia. It can be safely managed with fluid therapy alone if urine output is preserved, with progressive decrease of serum sodium as target. If this condition is recognized, outcome should be favourable.