A series of experiments was performed to investigate the previously-reported modulation of estradiol binding in female rat brain and pituitary gland by drugs that influence the dopaminergic system. Injection of the dopamine agonist, apomorphine, at minimum doses of 1-2 mg/kg body weight caused slight increases (in most cases, less than 10%) in the concentration of cytosol estrogen receptors in the mediobasal hypothalamus and anterior pituitary gland without influencing the concentration in the preoptic area. However, after subsequent injection of a saturating dose of estradiol, the level of nuclear estrogen receptors accumulating did not differ significantly between apomorphine-treated animals and vehicle-injected controls. These results extend, in part, previous reports that have shown an apomorphine-induced increase in the concentration of [3H]estradiol in brain and pituitary cell nuclei after an injection of [3H]estradiol. However, we failed to observe differences in the concentration of cytosol estrogen receptors as large as would be expected by previous work, and we failed to observe differences in the concentration of nuclear estrogen receptors after estradiol injection.