 The study hypothesis is that: Following perinatal asphyxia treatment with a combination of hypothermia and inhaled xenon preserves cerebral metabolism and structure. Following informed parental consent, infants that continue to require endotracheal tube ventilation following resuscitation will be randomised to treatment with hypothermia only or hypothermia and xenon. All infants in both groups will be treated with hypothermia for 72 hours started within 6 hours of delivery and infants allocated to hypothermia and xenon will also receive 30 xenon balanced with oxygen and air for 24 hours through a purpose designed delivery system. Structured neurological examination will be done daily during the 1st week after birth and at discharge. MRS and MRI will be performed once between 4-10 days of age. MRSMRI data analysis will be by investigators blinded to the allocated intervention. 