Induction of tyrosine aminotransferase using hydrocortisone was studied after administration of ethanol and CCl4 into animals. Administration of ethanol activated the enzyme. Simultaneous treatment of the animals with ethanol and hydrocortisone decreased 2-fold an inducing effect of the hormone. Within the subsequent periods the tyrosine aminotransferase activity continued to increase, exceeding the initial enzymatic activity induced by hydrocortisone. CCl4 did not affect the induction of the enzyme by hydrocortisone. The treatment with CCl4 showed an inducing effect with an increase in the enzymatic activity by 40% in liver tissue as compared with the initial level.