3-Hydroxyanthranilic, quinolinic and nicotinic acids 50 mg/kg, i.p. increased the content of rat blood plasma 11-hydroxycorticosteroids as well as the activity of liver tryptophan pyrrolase. After administration of anthranilic and picolinic acids, elevation in 11-hydroxycorticosteroid content was not followed by an increase in the tryptophan pyrrolase activity. Picolinic acid diminished induction of tryptophan pyrrolase activity by hydrocortisone and anthranilic acid did not affect the induction. Adrenalectomy prevented the increase in tryptophan pyrrolase activity after treatment with nicotinic, quinolinic and 3-hydroxyanthranilic acids. Prolonged augmentation of kynurenines in the organism might be a result of a mediated-through-corticosteroids increase in the tryptophan pyrrolase activity caused by elevation in the level of 3-hydroxyanthranilic, quinolinic and nicotinic acids.