The change in the substances related to energy source of the brain during running fit incited by 2-methyl-4-amino-5-hydroxymethylpyrimidine was investigated. There was no characteristic change in the brain glucose with the running fit but glutamic acid was reduced compared to before the attack. Glutamic dehydrogenase however, was not altered. Measurement of the free ammonia and glutamine of the brain showed that there was no rise during the running fit and this differs from the finding in other convulsive states.