Objective: To evaluate the effect of ultrafiltration on interleukins, TNF-alpha levels, and pulmonary function in patients undergoing coronary artery bypass grafting (CABG). Design: Prospective, randomized, controlled trial. Setting: University hospital. Participants: Forty patients undergoing CABG were randomized into a group assigned to receive ultrafiltration (UF) during cardiopulmonary bypass (CPB) or into another group (control) that underwent the same procedure but without ultrafiltration. Methods: Interleukins and TNF-alpha levels, pulmonary gas exchange, and ventilatory mechanics were measured in the preoperative, intraoperative, and postoperative periods. Interleukins and TNF-alpha also were analyzed in the perfusate of the test group. Measurements and Main Results: There were increases in IL-6 and IL-8 at 30 minutes after CPB and 6, 12, 24, and 36 hours after surgery, along with an increase in TNF-a at 30 minutes after CPB and 24, 36, and 48 hours after surgery in both groups. IL-1 increased at 30 minutes after CPB and 12 hours after surgery, while IL-6 increased 24 and 36 hours after surgery in the UF group. The analysis of the ultra filtrate showed the presence of TNF-alpha and traces of IL-1p, IL-6, and IL-8. There were alterations in the oxygen index, alveolar-arterial oxygen difference, deadspace, pulmonary static compliance and airway resistance after anesthesia and sternotomy, as well as in airway resistance at 6 hours after surgery in both groups, with no difference between them. Conclusions: Ultrafiltration increased the serum level of IL-1 and IL-6, while it did not interfere with gas exchange and pulmonary mechanics in CABG. (C) 2016 Elsevier Inc. All rights reserved.