Because the chronic exposure to the lung toxin Bleomycin can induce lung fibrosis in humans, and it is a classical method of inducing lung injury and fibrosis in mice [18],[24], we analyzed whether it induces lung fibrosis in mice expressing the dominant negative, nonphosphorylatable C/EBPβ-Ala217 transgene. This evidence concerns the gene CEBPB and pulmonary fibrosis.