A total of 37 different inactivated P. multocida vaccines either locally prepared or imported from other countries were tested for potency using both vaccination challenge test and ELISA assay. Correlation between both tests were evaluated and the minimum requirement for protection (70%) were matched with 2.25 X or more the cut off value of the both used kits. At the same time, ELISA antibody titer less than the cut off value was always associated with unsatisfactory protection rate. So, in conclusion, ELISA could be valuable in the evaluation of inactivated P. multocida vaccine through determination of the humoral immune response depending on the finding achieved in this study.