Objective To establish an animal model sensitive to SARS-CoV and study the pathogenesis of the disease.Methods Using RT-PCR and immunofluorescence assay(IFA) after virus islation and inoculation, SARS-CoV was examined in the lungs of young and aged ICR mice challenged by SARS-CoV.Pathological changes in the lungs and other organs of the two groups were examinined.The replication sites of virus in the lungs were analyzed by immunohistochemistry staining.Results Aged mice were more susceptible to SARS-CoV than young mice do.More severe diffuse alveolar damages were observed in aged mice.In addition,damages were observed in other organs of two aged mice such as degeneration,focal necrosis and vein dilation and congestion in liver,kidney and brain.Virus antigen was detected in alveolar epithelial and vascular endothelial cells.Conclusion Aged ICR mice may be used as a susceptible animal model for SARS-CoV in studies of mechanisms of SARS and evaluation of the effect of antiviral drugs and vaccines.