The data presented here are the first to describe the distribution of estrogen receptor-beta (ER beta)-like immunoreactivity in brain tissue. We employed an affinity purified rabbit antiserum made against a portion of the C-terminal of the ER beta protein. The majority of ER beta-like immunoreactive (ER beta-ir) neurons were found in the following regions: lateral septum, bed nucleus of the stria terminalis, paraventricular nucleus, supraoptic nucleus, medial amygdala, the dentate gyrus and the CA1 and CA2 fields of the hippocampus. A few ER beta-ir neurons were noted in the anterior hypothalamus, periventricular nucleus, medial preoptic area, and in the arcuate nucleus. All of the immunoreactivity appeared nuclear in its subcellular distribution, with the exception of the cells in the lateral septum, CA1 and CA2. In these areas immunoreactivity was noted throughout the perikarya and in cell processes. The data suggest that ER beta mediates estrogen's actions in a subset of hypothalamic and limbic neurons.