The effect of adrenalectomy (ADX) and corticosterone (CORT) replacement on neurotransmitter receptors was studied in dorsal hippocampus of rat using quantitative autoradiography. ADX for one week causes an increase in [3H]5-HT binding to 5-HT1 receptors which is significant in the CA1 cell field. CORT treatment of ADX rats for 3-5 days results in localized reductions of [3H]5-HT binding including a partial reversal of the increase observed after ADX in CA1. CORT treatment of ADX animals also decreases binding of [3H]QNB to muscarinic receptors in the dorsal hippocampus, with a significant effect in an area designated as subiculum. No influence of CORT was detected on [3H]prazosin binding to alpha 1 adrenergic receptors in dorsal hippocampus. Possible mechanisms for hormone effects on neurotransmitter receptor levels are discussed.