By means of brain perfusion method, for the purpose to study the effects of glutamic acid and its related amino acids on EEG, cerebral blood flow and systemic blood pressures, these amino acids were administered into the carotid system of perfused cat brains under a certain fixed condition and the intensity of each drug action was compared. The amino acids tested in the experiments were L-glutamic acid, L-aspartic acid, N-methyl-D-aspartic acid, N-acetyl-DL-aspartic acid, β-hydroxy-glutamic acid, L-glutamic acid-Na, L-aspartic acid-Na, and N-acetyl-DL-aspartic acid-Ca. For EEG, acidic amino acids induce transient excitatory changes followed by inhibition. These excitatory changes prove to be low-amplitude fast waves or burst of seizures, and postexcitatory inhibition to be slow waves or flat waves. N-methyl-D-aspartic acid, even in a minimal dose, induces marked bursts of seizures followed by L-glutamic acid, L-aspartic acid, L-glutamic acid-Na, and L-aspartic acid-Na, in their potency. Generally, N-acetyl-DL-aspartic acids show only low-amplitude fast waves but some of them do induce burst of seizures. β-Hydroxy-glutamic acid elicits only low-amplitude fast waves but never burst of seizures. N-Acetyl-DL-aspartic acid-Ca, differing from the free form, never induces excitatory changes. For the cerebral blood flow, acidic amino acids decrease the blood flow, but those that show a strong decreasing effect are N-alkyl amino acids such as N-methyl-D-aspartic acid and N-acetyl-DL-aspartic acid. On the Other hand, acidic amino acids increase the systemic blood pressure, and of them such an effect is especially marked with N-alkyl amino acid.