To investigate the location of estrogen-responsive neurons active in feedback processes, the effect of hypothalamic deafferentation upon gonadotropin (GTH) secretion was measured both by the morphology of intrasplenic ovarian grafts in ovariectomized rats and by radioimmunoassay of their serum GTH levels. Either complete or anterolateral deafferentation was performed with the anterior position of the knife cut varied over a 2-mm range. After either cut, luteinization of intrasplenic ovarian grafts was correlated with the precise location of the rostral portion of the deafferentation. As long as the knife cuts were positioned so as to include the region of the suprachiasmatic nuclei (SC) within the de-afferented hypothalamus, intrasplenic grafts were fully luteinized and serum levels of LH were comparable to those of control ovariectomized animals. If the knife cuts excluded the SC area from the deafferented hypothalamus, intrasplenic ovaries were polyfollicular and LH levels were significantly lower than in the control group. FSH titers were elevated above reported levels for the intact diestrous rat in all groups even though the morphology of the ovarian grafts was different, and no significant inter-group differences in FSH were observed. These data are consistent with the localization of important estrogen-responsive neurons within the SC region. Uterine weight and FSH measurements suggest that intrasplenic ovaries may secrete systemically-active levels of steroids, although at titers insufficient to alter the vaginal epithelium.