Atrial fibrillation (AF) is a common arrhythmia, after cardiac surgery, and it is associated with a twofold increase in cardiovascular mortality and morbidity. Reperfusion injury and inflammation associated with cardiac surgery are thought to be involved in its pathogenesis. Heat shock proteins (HSPs) are a family of chaperone proteins which assist in preservation of cellular integrity by maintaining proteins in their correctly folded state. The aim of this study was to investigate pre-postoperative heat shock protein70 (HSP70) and high-sensitivity C-reactive protein in serum from patients in preoperative sinus rhythm. We prospectively screened 45 consecutive patients admitted to the hospital for elective coronary artery bypass surgery (CABG). Electrocardiogram characteristics and cardiovascular risk profile were documented. Pre- and postoperative blood samples were collected. HSP70 value was 8.9 ± 4.8 ng/mL in Group A (study group) preoperatively and decreased to 7.7 ± 7.0 ng/mL postoperatively. In contrast, preoperative value of HSP70 was 4.2 ± 2.2 ng/mL and decreased to 2.7 ± 2.6 ng/mL postoperatively in Group B (control group). Statistical analysis showed significant difference regarding preoperative HSP70 levels in Group A compared to Group B. To our knowledge, with this study, the association of pre- and postoperative circulating HSP70 with postoperative AF was demonstrated for the first time. © 2008, Copyright the Authors.