The purpose of this study is to distinguish respiratory syncytial virus (RSV) infection and immunology between immunocompetent and immunocompromised murine and to explore immune mechanism of RSV infection. At various time points after RSV infection of BALB/c mice and nude mice, pulmonary viral titers were assayed, RSV antigen was tested by direct immunofluorescent assay and immunohistochemistry. Pulmonary mRNA expressions of Toll like receptor (TLR)2 and TLR4 were assayed by RT-PCR. CD4+ cells and CD8+ cells in peripheral blood were examined by flow cytometry and plasma total IgE was assayed by ELISA. Leukocytes in bronchoalveolar lavage fluid (BALF) and pulmonary histology were identified to reflect airway inflammation. It was found that RSV titers of both mice peaked on the 3rd day post infection with a much higher level of viral titer in nude mice than in BALB/c mice and a longer viral duration in nude mice (over 9 days post infection) than in BALB/c mice (6 days post infection). RSV infection induced higher viral antigen expression in nude mice (0.267 ±0.045) than in BALB/c mice (0. 168 ± 0.031). RSV infection enhanced pulmonary TLR4 expression of BALB/c mice (51.96% ± 11.34%) and nude mice (48.96% ± 12.35%) compared with each control (34.04% ± 10.06% and 32.37% ± 9.87% respectively). CD4+ peripheral blood cells increased in RSV infected BALB/c mice (66.51% ± 2.09% ) compared with the control BALB/c mice (51.63% ± 5.90% ), and CD4+ cells and CD8+ cells were deficient in nude mice. RSV infection increased plasma total IgE in both mice, and BALB/c mice had a larger amount of IgE on the 7th day post infection (9.02 ng/ml ± 2.90 ng/ml) and on the 14th day post infection (12.76 ng/ml ± 4.15 ng/ml) than corresponding nude mice (3.72 ng/ml ± 1.06 ng/ml and 7.62 ng/ml ± 3.08 ng/ml respectively on the 7th and 14th day post infection). RSV infected nude mice had more severe airway inflammation than infected BALB/c mice. It is concluded that BALB/c mice and nude mice presented similar RSV infectious characteristics. However, infection of nude mice showed higher viral titer with longer duration and more severe airway inflammation, lower level of plasm total IgE and CD4 + peripheral blood cells, but the similar pulmonary TLR4 expression with BALB/c mice.