SummaryWe studied electroencephalographically on the perfused cat brains both under glucose‐containing condition and glucose‐free condition, and discussed the relation between the electrical activity and metabolism of the brain. The results were as follows:1. In case of brain perfusion in which an anesthetic agent is used for premedication.a) EEG of both glucose‐containing cases and glucose‐free cases reveal high voltage spindle bursts that appear regularly, speak for that there exists a specific effect of the anesthetic agent used in premedication. From this result we would like to assume that by this perfusion method we stood in position to observe the brain function and metabolism under the influence of anesthetic agent.b) In the two cases of the brain perfusion there could not be recognized any essential differences in their EEG patterns. Shortly, EEG must have come in accord with the changes of brain metabolism.2. The brain perfusion under premedication with d‐tubocurarine, that is, under unanesthetized state.a) In the case of glucose‐containing perfusion it can be divided into three stages according to the changes of EEG of neocortex, and EEG pattern shifts from low voltage fast waves of 25–30c/s, 20–30pV to spindle bursts and then to irregular slow waves. Throughout this period the amygdala reveals low voltage fast waves, indicating dissociation of electrical activity between the amygdala and neocortex. At the hippocampus there appear first regular hippocampal slow waves but in response to the appearance of slow waves in neocortex its regularity is lost by increased fast wave components.b) In the case of glucose‐free perfusion there appear irregular low voltage spindle bursts in the neocortex, low voltage fast waves in amygdala, and likewise there appear in the hippocampus for a certain period of time regular hippocampal slow waves, proving dissociation of the electrical activity between the neocortex and the limbic system.c) In two modes of brain perfusion there can be recognized differences in EEG patterns as well as in the time of EEG appearance, whereby in the glucose‐free perfusion the EEG of neocortex disappears within 10 odd minutes or around 30 minutes after the commencement of the perfusion. In other words, by this method the presence or the absence of glucose in the perfused blood constitutes an important factor in the fluctuations of the neocortex EEG.d) By this method of the brain perfusion, seizure discharge occurs frequently at the site centered around the limbic system when the excitatory level of the brain is low and, as for the brain metabolism, there can be recognized an increase in the oxygen consumption and glucose uptake of the brain after the onset of seizure disharge.