AIM: To investigate the effect of rewarming in preterm infants presenting with hypothermia at admission. METHODS: The tissue oxygenation index (TOI), changes in cerebral blood volume (DeltaCBV) and changes in intravascular oxygenation (DeltaHbD) were measured in eight preterm infants, presenting with a temperature less than 35 degrees C at admission. RESULTS: A significant increase in HbD and TOI was seen in four patients (group A), while a significant increase in CBV and a decrease in HbD was seen in four other patients (group B). Retrospective analysis showed that group A had important signs of peripartal asphyxia. CONCLUSION: While infants with peripartal asphyxia showed an important increase in oxygenation during rewarming, no significant changes were seen in the non-asphyxiated infants.