Electroencephalograms (EEG) may provide detailed information about pathologic functional changes in the brain associated to focal lesions. Seizurogenic activity develops in many patients following focal brain injury and may be involved in the pathophysiological effects of brain trauma and stroke. Effects of diffuse traumatic brain injuries may be difficult to evaluate using histological examination or MRI. In this study we have examined the effects on the EEG of moderate air blast waves from explosions. A specially designed shock tube was used, in which anaesthetized rats were exposed to moderate air blast by the detonation of a charge consisting of non-electric detonating cap with a 1-3 grams PETN explosive at a distance of 1000 mm. In some experiments the effect of repeated detonation was studied. EEG was continuously recorded from 30 minutes after the detonation using pediatric scalp electrodes. Animals subjected to a shock wave from 1 g PETN showed minimal or small EEG changes, whereas the detonation of 2 g PETN induced a significant decrease in EEG. This effect was even more profound after detonation of 3 g PETN or a repeated detonation at the 2 g level. No epileptiform or seizure activities were recorded in the exposed rats or in age-matched control rats. These data indicate that EEG may be a useful diagnostic tool for the evaluation of acute effects of diffuse brain injuries and show that the effects of airborne blastwaves are dose dependent with regards to EEG depression.