Five-day-old rats subjected to prolonged asphyxia (at 37 °C) to the point of death showed an approximately 50-percent loss of brain ATP and a rise in ADP and AMP. Brain energy charge was reduced from 0.86 to 0.64. Recovery of ATP levels to normal was virtually complete 20 min after beginning resuscitation. Rats treated with dexamethasone (20 mg/kg body weight) showed, during asphyxia, a fall in brain ATP which was significantly less than in those animals asphyxiated without steroid. Possible implications for the use of glucocorticoid therapy in asphyxia neonatorum are discussed.