Abstract: Objective To determine the effects of estradiol and soy germ phytoestro gens on spatial learning and memory performance in ovariectom ized rats and to explore the possible mechanisms.Methods Ovariectomized Sprague-Dawley rats were randomly divided into four groups and assigned one of the following diets:basic diet,basic diet supplemented with phytoe strogens(0.4,1.6 g/kg diet) or 17B-estradiol(0.15 g/kg diet) for 12 weeks.The rats were evaluated for their spatial learning and memory performance with Morris water mazetask.The brain-derived neurotrophic factor(BDNF) and its tyro sine kinase receptors B(TrkB) receptor expression were measured.Results The rats supplemented with phytoestrogens and estradiol performed significantly better in spatial memory acquisition and retention compared to the controls.Escape latency (s)in rats supplemented with low-phytoe strogens(21.20±4.41),high-phytoe strogens(19.61±4.90) or estradiol(10.51±1.92) was significantly lower than that of the control(37.77±8.25).Trip distance(m) in rats supplemented with low phytoe strogens(3.62±0.69),high-phytoe strogens(3.76±0.60) or estradiol(2.43±0.57) was significantly shorter than that of the control(5.87±1.05).Estradiol or the high dose of phytoe strogens treamtent significantly increased the BDNF expression and mRNA level for TrkB recep to rs1Phy toestro gens did not showany significante strogenic-effect on the vaginal and uteri.Conclusion Phytoe strogens improve spatial memory performance inovariectomized rats.The memory enhance ment effect mayre late to the increased expression of BDNF and its TrkB receptor in the hippocampus.