By means of the brain perfusion slightly modified of the method by Geiger artificial blood with L-[U-(14)C]-alanine was perfused and circulatory disturbances was induced by such artificial decrease of brain blood flow. In this instance, alanine metabolism in the brain was compared with the metabolism observable during the standard brain perfusion. The results are briefly summarized as follows. 1) In the blood flow disturbing experiments where the blood flow was lowered by 43.0-60.0%. oxygen consumption, carbon dioxide formation and glucose uptake were markedly decreased, while the output of lactic acid from the brain was increased as compared with respective values in standard brain perfusion. 2) Despite the fact that there was no significant difference in the alanine concentration between the arterial and venous blood, there could be observed a significant decrease in the radioactivity of the venous blood when compared with that of arterial blood. This indicates clearly that alanine is being exchanged between the blood and brain. In addition, it has been demonstrated that the radioactivity of blood in the blood flow disturbing experiments was 3.8±1.10% as against 5.90±1.80% in the experiments of standard brain perfusion. 3) About 0.42-0.33% alanine in the blood was taken up and it was oxidized completely to carbon dioxide by the brain, showing no significant difference between the standard perfusion and blood flow disturbing experiment. 4) In the case of blood flow disturbing experiments there were observed a marked increase of lactic acid and an increasing tendency of alanine in the brain. 5) In both the standard brain perfusion and blood flow disturbing experiment alanine taken up by the brain within 70 minutes contained 50% of (14)C in the brain. In the latter experiments the rate of (14)C-incorporation into glutamic acid, aspartic acid and glutamine was decreased and its incorporation into lactic acid was increased. 6) In the blood flow disturbing experiment radioactivity in glutamic acid, aspartic acid, glutamine, alanine and lactic acid in the brain tended to decrease. The radioactivity of GABA was greater than that of glutamic acid, there could be observed a glutamic acid-GABA compartmentation phenomenon. just as in the experiments with [U-(14)C] glucose in the perfused blood.