Transient treatment with cytokines appears to improve hematopoietic function in Fanconi anemia; however, the effectiveness or adverse effect of long-term treatment is not known. The mitomycin C-treated Fancc(-/-) mouse provides a valuable model to address long-term efficacy of such treatment. Fancc(-/-) mice injected with granulocyte colony-stimulating factor, erythropoietin, or both cytokines showed a delay in mitomycin C (MMC)-induced bone marrow (BM) failure compared to untreated mice. However, long-term cytokine exposure followed by MMC challenges did not protect mice from the reduction of peripheral blood counts or the number of early myeloid progenitors. These results suggest that cytokine treatment may be beneficial only in the short-term, while long-term treatment is not protective for BM aplasia.