Strophanthin was shown to increase the blood flow in the external, internal zones of the cortex and the external medulla of the rat kidney without influencing the blood supply to the internal zone of the medulla. Contrikal eliminates the vasodilating effect of the drug in the mentioned zones of the renal tissue and significantly increases its natriuretic action. Indomethacin also prevents the hemodynamic shift occurring in the kidneys under the influence of strophanthin but fails to change the character of the natriuretic effect of the drug. Captopril exerts no influence on the increase of the blood flow in the external medulla but eliminates the vasodilating effect of strophanthin in the cortex and significantly potentiates its natriuretic action.