IBR is one of the most important contagious viral diseases in cow. The main purpose of this study was to develop an indirect immunoflourescent kit for detecting anti BHV-1 antibodies in bovine serum. Rabbit ant bovine immunoglobulin was obtained by immunizing 10 apparent healthy rabbit with bovine globulins. Ant bovine globulins were precipitated by using 45% ammonium sulphate and conjugated with FITC. For purification of conjugated sera we passed the sera through cephadex column and dyalized against PBS. We used purified and concentrated IBR virus as antigen. The most proper concentration of antigen for this purpose was i0-10 TCID5O of IBR virus propagated in R.BK cell line and purified and concentrated by ultra centrifuge at 80000g for 2 hours. To standardize such IFA kit, we examined a
1000 serum samples that were previously tested by SN. In comparison, we found the results by IFA and SN tests as follow: In SN test, out of 1000 tested samples 624 were positive (42.4%) but in IFA 632 were positive (43.2%). A number of 420 samples were positive in both tests. Four samples positive in SN and negative in IFA, 12 samples negative in SN and positive in IFA and 568 samples were negative in both tests. The correlation coefficient of the results obtained by two tests for detecting IBR infection was high about 98.4%. Because of simplicity, rapidity and lack of infectivity of this IFA test, we recommend this kit for detecting IBR antibodies in cow.