A minute quantity of α-hydroxy-γ-aminobutyric acid is detected in the brain of normal rabbit but on experimental loading of γ-aminobutyric acid via the carotid artery an increase in α-hydroxy-γ-aminobutyric acid was observed. It was found that α-hydroxy-γ-aminobutyric acid undergoes transamination and vitamin B_6 is involved in the reaction. The optimal pH for the reaction is about 8 and the reaction is inhibited by carbonyl reagenst. The enzyme is proved to be specific in the brain.