The present study was designed to investigate the correlation between the expression level of Hsp27 and Hsp72 and induction of apoptosis in HeLa cells in response to quercetin treatment. Treatment of HeLa cells with quercetin or with 1hr period of hyperthermia (42 degrees) increased the number of apoptotic cells. Inhibition of the expression of Hsp72 and Hsp27 in tumour cells by anti-sense oligonucleotides, enhanced the induction of apoptosis by quercetin. Heat shock itself had little effect on apoptotic cell death in these cells, but when combined with quercetin treatment, caused a significant increase in the number of apoptotic cells. These results suggest that the reduction of Hsps expression in the HeLa cell line promotes the induction of apoptosis by quercetin.