1. Guanidino compounds, taurocyamine, glycocyamine, α-N-acetyl-L-arginine, β-guanidinopropionic acid, γ-guanidino-β-hydroxybutyric acid, γ-guanidinobutyric acid, γ-hydroxyarginine, arginine and γ-guanidinobutyramide, were analysed by the automatic guanidino compound analysing system, based on liquid chromatography with an ion exchange resine LCR-1 (or Aminex A-5) column and Sakaguchi reaction. 2. The concentrations of taurocyamine, glycocyamine, γ-guanidinobutyric acid and arginine in rodent brain tissue were determind. On the other hand, five unknown peaks with positive Sakaguchi reaction were observed in the rabbit brain. 3. Guanidino compounds level in liver, kidney, serum and urine of rabbit were determined and compeared with in brain. 4. It was observed that γ-guanidinobutyric acid in the rabbit brain was increased, and on the contrary, taurocyamine, glycocyamine and arginine were decreased during convulsion induced by Metrazol injection. 5. Arginine and taurocyamine levels in the El-mouse were tended to increase atfer having the convulsive disposition.