After early experience with perioperative bleeding in sequential single-lung transplant recipients, aprotinin was introduced in an attempt to reduce this complication and the attendant morbidity. Records of sequential single-lung transplantations (n = 33) performed between January 1989 and November 1991 were reviewed to assess the impact of aprotinin on perioperative blood loss and blood product requirements. Recipients were divided according to whether or not they required cardiopulmonary bypass. In patients requiring cardiopulmonary bypass (n = 15), mean estimated postoperative blood loss was 3,000 +/- 500 mL in those who did not receive aprotinin (n = 4) compared with 1,177 +/- 253 mL in those who received aprotinin (n = 11) (p < 0.05). An average of 8.0 +/- 0.7 units of packed red blood cells were administered to patients not receiving aprotinin compared with 3.1 +/- 0.7 units to those who received aprotinin (p < 0.05). Requirements for fresh frozen plasma were similar in each group. There were no differences in blood loss or blood product replacement in the group not undergoing cardiopulmonary bypass (n = 18). Therefore, we conclude that aprotinin decreases postoperative blood loss and blood product requirements in patients undergoing sequential single-lung transplantation under cardiopulmonary bypass.