Several estrogenic compounds were examined for their abilities to stimulate the formation of adenosine 3’,5’-monophosphate (cyclic AMP) in incubated hypothalami from immature (27–28 day old) female rats. 17-β estradiol (E2) and diethylstilbestrol (DES) significantly increased the formation of cyclic AMP while estrone and estriol elicited small but not statistically significant increases in cyclic AMP formation. 17-α estradiol was ineffective in increasing cyclic AMP formation. The anti-estrogenic agent clomiphene was found to effectively antagonize the formation of cyclic AMP elicited by E2 and DES, while having no stimulatory effects on cyclic AMP formation itself. These data indicate that the binding of estrogenic compounds to cytoplasmic sites (receptors) in the hypothalamus is required for subsequent stimulation of cyclic AMP fo