Background: Inflammation plays a pivotal role in the pathogenesis of organ dysfunction after cardiopulmonary bypass (CPB). The aim of this study was to investigate whether pentoxifylline (PTX) has effects on the inflammatory process and leukocytes in cardiac surgery patients undergoing CPB. Material and methods: A double-blind, prospective, randomized, placebo-controlled study was undertaken to assess the effect of PTX on leukocyte counts, tumour necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and C-reactive protein (CRP) levels in 60 patients undergoing CPB for elective coronary artery bypass grafting. In 30 patients, 200 mg of PTX was added to 500 ml. NaCl and perfused for 180 min after induction of anaesthesia and also 100 mg of PTX was added to the warm cardioplegic solution; another 30 patients received saline solution as placebo. Results: All measurements were performed before PTX infusion (T0), after induction of anaesthesia (T1), 30 min after weaning from CPB (T2), and 6 hours (T3) and 24 hours postoperatively (T4). PTX did not change the percentage of eosinophils, basophils, neutrophils, monocytes, or lymphocytes, or CRP levels. In the control group, however, total leukocyte count and IL-6 level at T3 and T4 period were significantly higher than the study group. The progressive increment in TNF-alpha( level observed at each period was also significantly prominent in the control group. Conclusion: CPB-related whole body inflammatory response could be partially inhibited by intraoperative PTX administration. This effect of PTX would be helpful in preventing the well-known complications of CPB-induced systemic inflammation.