Ovariectomy (OVX) of female rats results in a decreased behavioral response to stimulation of the mesostriatal dopamine (DA) system and decreased striatal DA release in vitro. Estrogen replacement restores both behavioral and neurochemical responsiveness. In this report, microdialysis in freely moving rats is used to simultaneously study the behavioral and neurochemical effects of systemic estradiol. OVX rats received a unilateral 6-hydroxy-dopamine lesion of the substantia nigra and then underwent microdialysis of the intact striatum. Thirty min after a single injection of 5 micrograms estradiol benzoate, amphetamine-induced rotational behavior and striatal DA release are both potentiated, relative to the response of oil-treated control animals.