Dose-response curves were plotted to analyze the effects of adrenergic agonists and antagonists upon neural activity within the hypothalamus. Multiple unit activity (MUA) was recorded following microinjection of the drugs directly into the recording site through a hollow recording electrode. Dose-dependent decreases in MUA occurred following the microinjection of the alpha-adrenergic agonist 1-norepinephrine and also following low, but not high, doses of the alpha-adrenergic antagonist phentolamine. Neither the beta-adrenergic agonist dl-isoproterenol nor the beta-adrenergic antagonist dl-propranolol produced dose-related effects upon MUA at the sites tested. A small nonbiochemically specific decrease in MUA was also found to follow all microinjections into the lateral or ventromedial hypothalamus when any compound was microinjected, including isotonic saline.