In a canine model of open chest CPR, the effect of continuous intra-aortic balloon (IAB) inflation on cerebral and myocardial perfusion was investigated utilizing hemodynamic and radioactive microsphere techniques of assessing regional blood flow. Compared to deflation, IAB inflation augmented the following variables, expressed as percentage of prearrest control: aortic systolic (50% to 71%) and aortic diastolic (40% to 58%) pressures during 30-sec inflations; and epicardial blood flow (BF) (44% to 57%), mesocardial BF (40% to 56%), endocardial BF (36% to 50%), carotid BF (32% to 51%), and cerebral BF (67% to 88%) during inflations of greater than 150 sec. IAB inflation had no effect on right atrial pressure; thus, estimated cerebral and myocardial perfusion gradients were augmented. IAB inflation may prove to be a beneficial adjunct to open chest CPR.