Objective: This study examined the correlation between tumour necrosis factor-alfa (TNF-α), interleukin (IL)-6 and IL-8, IL-10 and methylprednisolone pretreatment. Methods: This is a prospective, randomized and double-blinded study. Sixty patients undergoing coronary artery bypass grafting (CABG) were randomized to receive either intravenous methylprednisolone (n = 30, Group M) or intravenous placebo (n = 30, Group S). The patients received intravenously either 30 mg/kg methylprednisolone (Group M) or placebo (Group S) 10 min before and after cardiopulmonary bypass (CPB). In an intensive care unit (ICU), four additional doses were given at 6-hourly intervals. Blood samples for the measurements of TNF-α, IL-6, IL-8 and IL-10 were obtained before induction of anaesthesia (T0 = control value), after induction (T1), before starting CPB (T2), after aortic declamping (T3), at the end of CPB (T4) and 6 hours (T5), 12 hours (T6) and 24 hours (T7) after skin closure. Creatine kinase (CK) and creatine kinase isoenzyme MB (CK-MB) were evaluated at the following intervals: T0, T5, T6 and T7. Results: When compared with the control value, TNF-α, IL-6 and IL-8 significantly increased in Group S and Group M (p < 0.05), but these values were significantly greater in Group S than in Group M (p < 0.05). In comparison with the control value, IL-10 increased in both groups (p < 0.05), but was significantly greater in Group M than in Group S (p < 0.05). CK and CK-MB were increased in both groups in postoperative values compared to control values. In Group S, CK and CK-MB levels were significantly lower than in Group M (p < 0.05). Conclusion: In this study, we have found that preoperative administration of methylprednisolone has decreased TNF-α, IL-6 and IL-8 release, and increased the perfusing IL-10 levels after CPB. Thus, methylprednisolone may decrease the inflammatory response during the CPB procedure. © Arnold 2004.