Fanconi anemia (FA) cells are hypersensitive to the cytotoxic and clastogenic effects of DNA cross-linking agents. Four complementation groups have been identified to date. The gene (FACC) that corrects the hypersensitivity of one of them, FA(C), has been cloned. In the present study, both the increased spontaneous and diepoxybutane (DEB)-induced chromosomal instability in FA(C) lymphoblastoid cells were corrected by transfection of FACC.