Normal perfusion pressure breakthrough is considered to be a great hazard during or after resection of large arteriovenous malformations (AVMs). This article presents the total blood flow to the AVMs, particularly those of greater than 3 cm in diameter (greater than 14.1 cm3 in volume), which have multiple compartments. The total blood flow into the AVMs in the sensory-motor area in 6 patients averaged 830 +/- 285 cc/min and those in the visual area in 4 patients averaged 358 +/- 33 cc/min. These flow values were compared to total flow through the intracranial arteries (756 cc/min). Large volume of blood flow into the AVMs carries a significant post-operative risk of normal profusion pressure breakthrough. Redistribution of blood flow from large AVMs into the cerebrovascular bed is an important factor for circulatory regulation to occur after their resection. The risk of normal profusion pressure breakthrough must be minimized by surgical technique discussed in the text.