||Endocrine disrupting compounds pollute the environment and are thought to play a role in human reproductive disorders and hormone-dependent cancers. This study investigated the development of a novel in vivo model to better screen and assess the effects of these compounds. Ovariectomized adult female mice received bisphenol A (BPA) or BPA and 17β-estradiol in combination via oral gavage for seven consecutive days. To determine estrogenic activity, uterine wet weights were recorded and RT-PCR used to measure expression of estrogen-regulated genes in the uterus and mammary gland. BPA alone did not induce an estrogenic response. Although co-administration of BPA and 17β-estradiol did not produce a dose-dependent increase in INDO mRNA expression in the mammary gland, co-administration significantly increased uterine weights and showed a trend towards increased C3 mRNA expression in the uterus relative to estrogen treatment alone. These results demonstrate that this is a good model to test endocrine disrupting compounds.