Fanconi anemia (FA) is an autosomal recessive disorder that leads to aplastic anemia. Cells from FA patients are abnormally sensitive to DNA cross-linking agents such as mitomycin C. FA consists of at least five subgroups (FA-A through-E). The genes defective in the FA-C and FA-A groups have recently been cloned. Transfection of the normal FA gene into mutant cells corrects the hypersensitivity to DNA cross-linking agents and improves cell viability in vitro. The function of the FA gene products is still unclear, however. For patients lacking a compatible bone marrow transplantation donor, an experimental trial of gene therapy for group C FA is ongoing at the National Institutes of Health.