In liver tissue of rats, a conventional laboratory food of which was substituted for galactose-rich food, the galactokinase activity was increased, but the glucokinase was not affected. In the rats kept on a glucose-rich food the glucokinase (but not the galactokinase) was activated. Hydrocortisone injection induced an increase in tyrosine aminotransferase, but the galactokinase activity was not altered. The data obtained suggest that in rat liver tissue the galactokinase was specifically induced under the effect of galactose. Except for the liver tissue, galactose induced galactokinase in eye crystalline lens; the enzyme activity was not altered in spleen and kidney.