Fanconi anaemia (FA) patients show cellular sensitivity to a variety of clastogens and prominently to cross-linking agents. Although there is a long-standing clinical impression of radiosensitivity, in vitro studies have yielded conflicting results. In this study, initial radiation-induced DNA damage and kinetics of DNA repair in (60)Co gamma-irradiated leukocytes from healthy volunteers, FA patients and heterozygotes were assessed using alkaline comet assay. Results showed higher levels of baseline DNA damage in leukocytes of patients and heterozygotes than in controls. Gamma-ray-induced initial DNA damage in leukocytes of FA cases was not significantly different from that of healthy donors and heterozygotes. However, after a repair time of 4 h, following irradiation, samples from the healthy individuals and carriers showed less residual DNA damage in their leukocytes, whereas FA patients revealed more DNA damages than their baseline. Although similar initial induced DNA damage was observed for all groups, the repair kinetics of radiation-induced DNA damage of leukocytes from FA patients was statistically different from healthy and carrier subjects. These findings may suggest that hypersensitivity of FA cells to cross-linking and clastogenic agents might be due to inefficient and delayed repair machinery of these cells. Also, the amount of residual DNA damage after irradiation could be used as a putative predictor of FA screening and cellular radiosensitivity.