Abstract: The role of heat shock proteins in AF pathophysiology was investigated in this study. We analysed mRNA and protein expression of heat shock protein (Hsp) 70, Hsp 60 and Hsp 27 in two groups of patients undergoing cardiac surgery. The first group (NAF) included six patients with coronary heart disease and no AF, the second group (CAF) included six patients with coronary heart disease and chronic atrial fibrillation. There were no significant changes in Hsp 70 protein or mRNA expression. In CAF group Hsp 60 protein and mRNA expression was also unaltered compared to NAF. Hsp 27 mRNA expression showed a significant decrease of 16±5% (NAF vs. CAF) yet accompanied with no statistically significant change of protein expression. The protein expression of Hsp 27, Hsp 60 and Hsp 70 was not altered significantly in patients with chronic AF. In contrast to heart failure, heat shock proteins seem to play a minor role in AF pathophysiology.