Background/Aim: The aim of this study is to determine the quantitative expression of the bacterial heat shock protein, Chaperonin-60 (Cpn60) and pro-inflammatory and anti-inflammatory cytokine in periapical tissue, obtained from individuals with chronic periapical lesions and to determine the correlation between the expression of the bacterial heat shock protein and the expression of these cytokines. Methods. The study was performed on 18 periapical lesions and 6 control samples of healthy periapical tissue, taken at the Clinic of Dental Medicine, Faculty of Medical 4 Sciences University of Pristina, Kosovska Mitrovica. The levels of mRNA expression of pro- and anti- inflammatory cytokines and bacterial heat shock protein were determined by real time quantitative RT-PCR. Results. Analysis revealed significantly higher mRNA levels of TNF-? and Cpn60 in the tissue of periapical lesions compared with normal periapical tissue (P <0.05). Contrary to these results, the mRNA expression of anti-inflammatory IL-10 was significantly higher in the samples of normal periapical tissue compared with the mRNA levels of this cytokine in the tissue of periapical lesions (P <0.001). Expression of Cpn60 is in strong correlation with TNF-? expression in periapical lesions. Conclusion. Cpn60 released from bacteria in periapical tissue could be a strong stimulator of inflammatory response and one of the important players in the pathogenesis of periapical lesions.