Since our initial experience on April 28, 1989, a total of nine patients have received treatment for giant cerebral aneurysm using cardiopulmonary bypass with deep hypothermia and circulatory arrest. The following data summarize our findings associated with these patients. The average patient's age was 46 years (range: 16 to 59 years of age). Seven patients were female, two were male. The procedure required approximately eight hours to complete with an average cardiopulmonary bypass time of 104 minutes (range: 60 to 140 minutes). Circulatory arrest time averaged 26 minutes (range, 12 to 45 minutes) with an average of 30 minutes (range: 10 to 62 minutes) required to cool the patient to below 18 degrees C (64 degrees F). An average of 54 minutes (range: 28 to 81 minutes) was required to warm the patient to a bladder temperature of 36 degrees C (96.8 degrees F). During the cooling period, five patients went into asystole spontaneously, four patients required bolus of 20 mEq of potassium chloride, and upon rewarming, spontaneous defibrillation occurred in six patients. Three patients were defibrillated without difficulty with external shock. The average number of blood products administered in each of the nine patients was 3.6 units of packed red blood cells, 3 units of fresh frozen plasma, and 6.5 units of platelets. Six patients recovered postoperatively without complication, and the recovery of three patients was affected by the complex anatomical location of the giant aneurysm. Cardiopulmonary bypass with deep hypothermia and circulatory arrest offers an alternative approach to the treatment of giant cerebral aneurysms considered inoperable by conventional techniques. The effectiveness of each procedure depends on the collaborative efforts of every member of the perioperative nursing team, the neurosurgical team, the cardiac surgical team, the neuroanesthesiology team, and the perfusionists. Careful planning and anticipation at every stage of the surgery can reduce surgical time, cardiopulmonary bypass time, and most importantly, circulatory arrest time.