To develop more specific and sensitive diagnostic methods for infectious bovine rhinotracheitis, 7-C-2 monoclonal antibody specific to polypeptides of infectious bovine rhinotracheitis virus (IBRV) was applied in indirect immunofluorescence antibody assay (IFA), indirect immunoperoxidase assay (IPA) and radial immunodiffusion enzyme assay (RIDEA). It was found that IBRV infected in MDBK cells could be detected as early as 8 hours post infection by IFA, and that IFA was more rapid and specific to identify IBRV antigen than IPA. The diagnostic efficacy of RIDEA and SN test was studied with 88 bovine sera. It was evident that RIDEA could eliminate the false positive reaction encountered in serum neutralization (SN)test, being more rapid and sensitive than the latter. Highly significant correlation coefficiency (r= 0.76, p0.01) was evaluated between the titers of sera and the diameters of RIDEA. Tracheal membranes and sera collected from 96 slaughtered cattle with lesions in respiratory organs were examined to detect IBRV antigen and antibody by IFA, RIDEA and SN test. It was presented that positive rates were 32.3 % in IFA, 20.8 % in RIDEA and 21.9 % in SN test, and that coincidence rate between RIDEA and SN test were 100 % in positive sera and 98.7 % in negative sera. In conclusion, it was assumed that application of monoclonal antibody could improve the diagnostic efficacy of IBR by enhancing sensitivity and specificity of IPA, IFA and RIDEA