Abstract The regional cerebral metabolic rate for glucose (rCMRgl) was autoradiographically measured in conscious rats during 180–210 min of exposure to 3 atmospheres absolute oxygen (ATA O 2), 3 ATA N 2-O 2 normoxia and air at 1 ATA. The exposure time and oxygen pressure in the present study were purposely matched to a parallel project in human subjects. The electrocorticogram (ECoG) was continuously recorded throughout the exposure. According to the ECoG responses, the oxygen-exposed rats fell into two categories: (1) ‘resistant’ ones, those without changes in ECoG throughout the exposure; and (2) ‘sensitive’ rats, those with changes in EcoG before or during the rCMRgl measurements. The observed ECoG changes were increased slow wave activity in the δ range, which was in some cases followed by paroxysmal electrical discharges. No changes in rCMRgl were observed in oxygen-exposed ‘resistant’ rats as compared to air breathing or N 2-O 2 normoxic rats at 3 ATA. However, in the ‘sensitive’ rats there were increases in rCMRgl in 8 of the 28 neuroanatomical structures examined as compared to the air breathing and 3 ATA normoxic controls. It is concluded that the increase in rCMRgl are related to the onset of the oxygen-induced preconvulsive changes in ECoG.