© Copyright 2016 by Gazi University Medical Faculty.Objective: Cardiopulmonary bypass (CPB) triggers systemic inflammation. Inflammatory system activation may cause deteoriation in liver and renal functions. In our study we aimed to search the effect of on-pump CPB and beating heart off-pump coronary artery bypass grafting (CABG) surgery techniques on renal and liver functions. Methods: Sixty four patients who underwent coronary artery surgery were included in the study and were divided into two groups: on-pump CPB group (40) and beating heart off-pump CABG group (24), prospectively. The blood samples were collected for preoperative and postoperative levels of blood urea nitrogen (BUN), creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and AST to ALT ratio at 24th and 48th hours. Results: Clinical and demographic features were similar in both groups. There were no statistically significant difference in levels of preoperative BUN, creatinine, AST, ALT, AST to ALT ratio. The postoperative 24th hour plasma levels of creatinine, AST and AST/ALT were lower in beating heart off-pump CABG group but BUN and ALT levels were similar among the two groups. The postoperative 48th hour plasma levels of BUN, creatinine, AST and AST/ALT were lower in beating heart off-pump CABG group but levels of ALT were similar in both groups. Conclusion: Based on our findings we conclude that beating heart off-pump CABG has lower negative effect on liver and renal function than on-pump CPB. Abstract of this manuscript was presented in 7th Congress of Update in Cardiology and Cardiovascular Surgery in association with TCT Mediterranean as a poster.