['To evaluate the effect of physiological dose 17-β-estrodiol (E2) replacement therapy on vascular dementia caused by cerebral chronic hypoperfusion.', 'The rats with bilateral common carotid artery occlusion (BCCAO) received E2 treatment starting from 3 days or 3 months after the operation. IgG leakage into the brain parenchyma and the changes of microvascular ultrastructure following BCCAO were examined using immunohistochemistry and electron microscopy, respectively; Western blotting was used to detect the expression of vascular endothelial growth factor (VEGF) protein.', 'Compared with the sham-operated groups, the rats at 3 days and 3 months after BCCAO showed extensive vascular damages surrounded by IgG immunoreactivity in both the cortical and hippocampal CA1 regions. Stronger IgG immunoreactivity in the hippocampal CA1 region was observed at 3 days after BCCAO than at 3 months, but no significant IgG leakage was found in rats with continuous E2 treatment. Electron microscopy revealed severe edema around the blood vessels, mild vascular dilation, and endothelial cell damages at both 3 days and 3 months after BCCAO. E2 treatment markedly reduced the microvascular ultrastructural damages. Western blot analysis showed a significant increase in VEGF expression in the CA1 region at 6 h and 1 day after BCCAO followed by an obvious reduction till reaching the lowest level at 3 days; VEGF expression remained low even at 3 months after BCCAO and was significantly increased by E2 treatment.'] Does [ Estrogen decrease vascular damage induced by chronic hypoperfusion through upregulating VEGF expression ]?