Two experimental models of brain edema have been produced in rats. Some animals underwent bilateral carotid artery ligation (BLCL), while others received extradural compression by a rubber bar. The characteristics of these conditions were compared by Evans blue injection and by the colloidal carbon perfusion method. Although both models produced an increase in the water content of brain tissue, a blood-brain barrier leak to Evans blue was observed only in the compression edema model. The steroid drug, hydrocortisone, diminished the water content of the edematous brain caused by compression but had no effect on that produced by BLCL. The cerebral circulation, as studied by colloidal carbon perfusion, revealed a vasodilation pattern in those animals who underwent bilateral carotid artery ligation, while vascular damage was observed in the compression edema model.