The development of learned aversions to the available diet has been shown to contribute to the anorexia and weight loss which accompany the growth of certain tumors, including the Leydig LTW(m) tumor. Estradiol infusions were found to closely mimic the effects on food intake and food preference seen after Leydig LTW(m) tumor implants. That is, reductions in food intake and the development of severe aversions to a target diet available during hormone infusions were seen. Lesions of the area postrema greatly attenuated these effects of estradiol infusions. Similar lesions have been shown to have parallel effects on the LTW(m) tumor syndrome. These findings strongly implicate the elevations of circulating estrogens which accompany the growth of LTW(m) tumors in generating the symptoms of anorexia and diet aversions.