The author estimated the effect of hypophysectomy on the transaminase activity in the brain and liver of the Wister albino rat. The activities determined were aspartate-glutamate (AsGT), alanine-glutamate (AlGT), and γ-aminobutyrate-glutamate (γAGT) transaminases. The activities of AsGT and γAGT increased remarkably in the brain and liver of the hypophysectomized rat. The AlGT activity of these organs did not change under the same condition.