Background: In addition to malignant diseases, acute and chronic inflammations may elevate plasma levels of tumor markers CA 125 and carcinoembryonic antigen (CEA). Cardiopulmonary bypass (CPB) causes a generalized inflammatory response. In this study, we have investigated the effect of CPB on plasma levels of CA 125 and CEA. Methods: We measured plasma levels of CA 125 and CEA in patients undergoing coronary artery bypass grafting (CABG) with CPB (Group 1, n = 21), and in patients who underwent off-pump CABG, that is, without CPB (Group 2, n = 16). Blood samples were collected preoperatively, and on postoperative days 1, 6, and 12. Results: Within both groups, CEA plasma levels were not significantly influenced in any samples. Comparing with preoperative values, CA 125 values elevated significantly on postoperative days 6 and 12 within both groups. It was observed that the elevation of CA 125 plasma levels in these samples were significantly higher in Group 1. Conclusions: The results indicate that CPB elevated plasma level of CA 125. However, clinical importance of this finding needed further evaluation.