To determine whether the [14C] aminopyrine breath test (ABT) predicts surgical risk in patients with liver disease, it was obtained prior to various surgeries in 38 patients with known or suspected liver disease. A modified Child's classification was also determined. Six of the seven operative deaths (three Child's A, two B, two C) had ABTs less than 2.3%, while 30 of 31 survivors (24 Child's A, seven B) had ABTs greater than 2.3% (p less than 0.000018). Seven of the 16 patients with normal ABTs had biopsy-proven cirrhosis and had postoperative courses indistinguishable from the remainder of the group. We conclude that surgery in patients with ABTs less than 2.3% is associated with extremely high mortality. In addition, cirrhotics with normal ABTs tolerate elective surgery well.