AIM: To determine the role of the glycocalyx in microvascular permeability. METHODS: Dextran was intravenously injected and quatitatively examined in the rat transient cerebral ischemic model. At the same time, endothelial glycocalyx (anionic sites) was labelled with the probe cationic gold colloid (CGC) using post-embedding technique and examined with electron microscope. RESULTS: The labeling of CGC decreased significantly following ischemia, meanwhile, microvascular permeability to dextran increased. CONCLUSION:Endothelial glycocalyx is very sensitive to ischemia or anoxia. Its disruption may be the initiator of the dysfunction of endothelium and the determinant of increased permeability.