Background: Neutrophil activation is related with myocardial ischemia/reperfusion and CPB. Aim: The aim of this study was to compare the influence of both systemic and myocardial ischemia and CPB on β-glucuronidase and myeloperoxidase release during different types of CABG. Material and methods: 53 patients randomised into 3 groups. Group A: 16 patients CPB with aortic clamping. Group B: 18 CBP on beating heart. Group C: 19 patients off-pump procedure. Plasma for analysis was obtained from the radial artery and cephalic vein before CPB installation (in groups A and B) or before the first distal anastomosis in the off-pump group. Further samples were taken immediately after aortic declamping (group A) or after the last distal anastomoses (groups B, C), and after 30 min. of reperfusion (group A) or 25 min. after last distal anstomoses in off-pump groups B and C. Results: The highest β-glucuronidase concentration was found in group B in samples taken immediately after last distal anastomosing. The highest myeloperoxidase concentration was found in samples obtained in group B in samples taken 25 min. after the last distal anastomosing, Conclusions: CABG with CPB on beating heart results in highest neutrophil activation.