The spatiotemporal properties of electroencephalographic (EEG) burst activity were examined by recording epidural EEG simultaneously at eight loci over the cerebral cortex of the rat with four electrodes arranged anteroposteriorly or mediolaterally in each hemisphere. EEG showed a burst suppression pattern consisting of alternate high frequency oscillation and silent states under deep anesthesia induced by 3.5-4.0% sevoflurane. Duration of bursts increased and silent state periods decreased under less deep anesthesia induced by 3.0-2.5% sevoflurane. Burst suppression cycles were synchronized and the shape of bursts was similar at all eight recording sites. Cross-correlation values were calculated between all intra- and interhemispheric pairs of EEG signals with a time period of 50-60 s as an index of similarity of EEG signals. The values of each EEG pair did not change significantly during the entire recording period with changes in anesthesia levels. The values linearly decreased with greater distance between recording sites in each hemisphere irrespective of anteroposterior or mediolateral electrode arrangement. The cross-correlation values were larger between interhemispheric EEG pairs recorded at symmetrical sites with the anteroposterior electrode arrangement, and recorded at medial portions of both hemispheres with the mediolateral electrode arrangement. Amplitude of bursts was greater in EEG signals recorded at the central locations in the cortex, that is, the primary somatosensory area. These findings indicate the basic spatiotemporal characteristics of neocortical burst activities in anesthetized rats.