Under study was the tritium distribution in tissues of the neuroendocrines system, liver and muscle after intravenous injection into female rats of an aqueous-lipid emulsion containing 3H-DMBA in a dose of 0.05 mci/kg. Thirty minutes following the injection the specific radioactivity of the liver, endocrinous glands, anterior and mediobasal hypothalamus tissues was higher than that of the cerebral cortex, dorsal hypothalamus. Label incorporation into the mediobasal hypothalamus was maintained at a higher level during 12 hours after 3N-DMBA administration than in the anterior and medial hypothalamus, cerebral cortex or muscle. A preliminary injection of adebit or I-DOPA failed to influence the character or rate of tritium uptake by tissues 30 minutes, after the labelled carcinogen was injected. The significance of DMBA retention in the hypothalamus for the mechanism of its action on the neuroendocrinous system is discussed.