The authors describe an experimental model of transient (15 min). unilateral, cerebral ischemia followed by 60 min of reperfusion in anesthetized rats. Zones of non perfusion are recorded and referred to as the "no-reflow phenomenon". The authors believe that vascular changes which interfere with postischemic reperfusion are due to ischemia-induced swelling of perivascular glia. The effects of the intracarotid injection of dexamethasone, furosemide and escina are evaluated in the attempt to show the importance of brain edema in ischemic cerebral damage.