To investigate the association between the progressive stage of cervical dysplasia and DNA damage by comet assay. A hospital-based, unmatched, case-control study was performed. DNA damage levels (none, low, medium and high) in the cervical epithelial cells of 31 women (10 with low grade squamous intraepithelial lesions [LSIL], 10 with high grade [HSIL] and 11 with no cervical lesion) were evaluated using the comet assay. A significant increase in medium DNA damage was observed in women with HSIL (17 +/- 8.9) relative to that in the control women (9 +/- 6.1). A significant increase in high DNA damage was also observed in women with LSIL (23 +/- 15.4) or HSIL (32 +/- 13.1) relative to that in the control women (12 +/- 7.9). These findings confirm that the grade of a cervical lesion correlates with the degree of genomic instability.