Steroid hormones provide a means of coordinating the activity of widespread neural systems that mediate endocrine, autonomic, and somatomotor aspects of reproductive processes that are essential for the propagation of mammalian species. Because these processes are quite different in each sex, the neural pathways that control them are also sexually differentiated. The anteroventral periventricular nucleus (AVPV) of the preoptic region occupies a nodal point in sexually dimorphic forebrain circuits and appears to play a critical role in regulating gonadotropin secretion. The AVPV contains sexually dimorphic populations of opioid peptide containing neurons that display different patterns of development and are differentially regulated in adult animals by gonadal steroids. Moreover, estrogen (ER) and progesterone (PR) receptors are expressed in AVPV neurons in a transmitter-specific way, and the expression of these nuclear transacting factors is differentially regulated by sex steroids. Thus, neurons in the AVPV show distinct patterns of hormonal regulation of gene expression, and distinct hormone receptor profiles.