Control and ethanol-intoxicated rats were given a small air embolus in the right common carotid artery after ligation of the external carotid branch. The extravasation of Evans blue-labelled albumin (EBA) was studied. Control rats dispalyed a slight extravasation of EBA through arteries and arterioles at the surface of the right hemisphere with a slight spread into adjacent brain parenchyma. Additionally, ethanol-intoxicated rats showed a great leakage through small blood vessels even deep in the right hemisphere and a blue-staining of most of the embolized hemisphere. Thus it was shown that during embolization, ethanol increases the vascular permeability to macromolecules. It is proposed that this phenomenon mainly is due to injury to the endothelial cells.