Early experience with aprotinin in deep hypothermic circulatory arrest (DHCA) raised alarm about hazards associated with its use. Based on what little is known about possible mechanistic interactions between hypothermia, stasis, and aprotinin, there is no evidence that aprotinin becomes unusually hazardous in DHCA. Excessive mortality and complication rates have only been reported in clinical series in which the adequacy of heparinization is questionable. Benefits associated with use of aprotinin in DHCA have been inconsistently demonstrated. The only prospective, randomized series showed significant reduction in blood loss and transfusion requirements. Use of aprotinin in DHCA should be based on the same considerations applied in other cardiothoracic procedures.