The effect of thyroliberin on syntheses of beta-endorphin and corticotropin were studied on the cats under anesthesia (Nembutal(R): 40 mg/kg, iv) in blood plasma (BP) and cerebral-spinal fluid (CSF). The BP and CSF were withdrawn from jugular vein and thoracic region at the 3(rd) and 20(th) minutes before and after the giving of thyroliberin. Thyroliberin made no change on the level of beta-endorphin in every two medium. At the beginning plasma level was 47 3.3 p mol/L. After 3 and 20 minutes, they were found 42+/-8.2 and 45+/-10.5 p mol/L. In spinal fluid it was found 1.3+/-0.4 p mol/L. After thyroliberin, the levels were 1.8+/-0.4 and 1.8+/-0.5 p mol/L. In plasma, the level of the corticotrophin increased in %75+/-18 at 3 and 20 minutes, whereas in the spinal fluid, thyroliberin decreased the corticotrophin as well as %41+/-1.3 and %63+/-9.1.