There were differences in cell number, apoptotic cell proportion, and the Ki-67 labeling index between the 15 Gy and 30 Gy groups after liver irradiation; the TGF-β1 and α-SMA expression results might support the gradual progression of radiation-induced liver fibrosis over the 40-week period following irradiation, even in the 15 Gy group. The gene discussed is MKI67; the disease is Hepatic fibrosis.