In the present study, analysis of lung serial sections of bleomycin- induced pulmonary fibrosis in mice as well as UIP areas in lung biopsies undertaken for IPF diagnosis evidenced the co-expression of HIF-1α and CHOP in hyperplastic AECs covering the remodeled parenchymal air spaces. The gene discussed is HIF1A; the disease is idiopathic pulmonary fibrosis.