There have been several reports in the literature about hypernatraemic dehydration and severe malnutrition in exclusively breastfed infants. The authors report a series of four such cases admitted to the Newborn Special Care Unit of the University Hospital of the West Indies over a seven-year period. All four were term infants who had weight loss of greater than 20% of their birthweight, serum sodium levels greater than 175 mmol/L, metabolic acidosis and pre-renal failure at presentation. Three of the infants had seizures shortly after presentation. One of the infants died soon after admission to hospital, the three others had normal neurological development clinically at the time of last review.