Radiation-induced DNA damage and kinetics of DNA repair was evaluated in three human ovarian carcinoma cell lines (i.e. CH-1, A-2780 and SKOV-3) with different sensitivities to ionizing radiation and radiation-induced apoptosis with the aid of single cell gel electrophoresis (SCGE, the comet assay). A good correlation was found between the initial level of DNA breaks and radiation induced apoptosis in CH-1 and SKOV-3 cell lines. While the radiation-sensitive CH-1 cell line manifested the highest level of initial DNA breakage and a significant delay in DNA break rejoining, the inverse correlation was found in the radiation-resistant cell line SKOV-3. Intermediate initial level of breaks was induced in the A-2780 cell line characterized by the intermediate sensitivity to X-ray radiation in comparison to CH-1 and SKOV-3 cells, however, the kinetics of DNA repair was comparable with radiation-resistant cell line SKOV-3. Our data suggest that the comet assay could be a promising tool for prediction of intrinsic cell radiosensitivity. This method might be considered as a supplementary technique to the more reliable but time consuming clonogenic assay.