This study examines the relationship between core temperature and whole body energy expenditure, cerebral oxygen consumption (CMRO2), cerebral blood flow (CBF), and intracranial pressure (ICP) in severely head injured children. A total of 107 serial measurements of temperature, energy expenditure, CMRO2, CBF, and ICP were made in 18 head injured children receiving neurointensive care. Energy expenditure was measured using indirect calorimetry, and CMRO2 and CBF using the Kety-Schmidt technique. The mean rectal temperature was 37.8 degrees C (34-39.1 degrees C) despite modification with paracetamol. Within each child there was a positive relationship between rectal temperature and energy expenditure, energy expenditure increasing by a mean of 7.4% per degree C. There was no evidence of significant relationships between rectal temperature and CMRO2, CBF, or ICP. Mild induced hypothermia in two children did not result in decreased CMRO2 or CBF measurements. The efficacy of interventions aiming to modify cerebral energy metabolism by changing core temperature cannot be readily assessed by the response of the whole body.