Effects of estradiol benzoate (EB) on [3H]paroxetine binding in dorsal hippocampus and cerebral cortex of gonadectomized male and female rats were evaluated by quantitative autoradiography. EB significantly decreased [3H]paroxetine binding in male and female rats in the oriens layers of CA1-CA4, and in the radiata/lacunosum moleculare layers of CA2 and CA3. Sex differences were also noted, with binding of [3H]paroxetine being significantly lower in female rats in the radiata/lacunosum moleculare layers of CA2 and CA4, and in the suprapyramidal dentate. No significant effects of either EB or sex were noted in the cortex.