Objective: In this study, tumor necrosis factor-α (TNF-α) and C-reactive protein (CRP) levels which are important in inflammatory response to off pump and on pump coronary by-pass surgery, were compared and their clinical reflections were examined. Study plan: Forty patients who underwent coronary artery by-pass grafting in our clinic, were included in the study. The first group included on-pump patients (Group I, n=20) and second group included off pump patients (group II, n=20). In both groups the day before surgery and post operative sixth hour of tumor necrosis factor, as well as the day before surgery, post operative first and third days of C - reactive protein levels were measured. Results: In the comparison of TNF- α levels, while the preoperative levels were not significantly different in both groups (p=0.098), postoperative levels of Group 1 were significantly higher (p=0.016). In both groups any significant difference between pre operative CRP levels (p=0.074) was not found. In Group I, the first and third postoperative day CRP levels were significantly higher (p=0.021-p=0.019). White blood cell levels of each group at preoperative (p=0.094), post operative 1st day (p=0.091) and post operative 3rd day (p=0.095) were not significantly different. Conclusion: As an indicator of inflammatory response, the tumor necrosis factor- α and Creactive protein levels were significantly higher in operations using cardiopulmonary by-pass than surgeries on beating heart. © 2012 Düzce Medical Journal.