To determine the efficacy of cerebral microcirculation promoting therapy in postischemic brain failure, 11 dogs awakening from methohexital sodium anesthesia were subjected to 12 minutes of reversible circulatory arrest by ventricular fibrillation. Physiological variables were controlled for six hours after resuscitation, and the dogs were observed for seven days. Six dogs without the special postresuscitative therapy did not awaken, and either died within 36 hours or remained comatose for seven days. In five dogs, a combination of the following measures was applied: (1) mean arterial pressure was raised to 150 to 180 mm Hg with norepinephrine for six hours; (2) heparinization; (3) rapid intra-aortic injection of dextran 40 (10 ml/kg body weight); and (4) normovelemic hemodilution with dextran 40 to a hematocrit reading of 25% to 30%. All five treated dogs awakened within 24 hours and appeared normal on the seventh day. Therapy enhanced constriction of pupils and normalization of the electroencephalogram (P less than .05). Postischemic neurological deficit is at least partially due to impaired reperfusion and can be ameliorated or prevented by blood flowing-promoting therapy.