Objectives: Infectious bursal disease (IBD) is an acute, highly contagious and immunosuppressive disease in chickens which can be controlled by vaccination. So far all IBD vaccines in Iran market are imported. Recently production of an intermediate live IBD vaccine, registered by Razi Vaccine and serum Research institute, has been launched. To complete vaccine master file, several clinical trials were conducted in six provinces covering different geographic regions of Iran. Material &Method: Six broiler farms, located in Khorasan Razavi, Ilam, Fars, Khozestan, Mazandaran and West Azarbayjan provinces were selected. In each farm, two houses with the similar condition were chosen. Two different brand of vaccines, including Razi (test) and a commercial brand (control) were used. According to the level of maternal antibodies, vaccines were administered once or twice in drinking water. The criteria for assessment of the vaccines were based on several items including: antibody response to IBD, ND and AI vaccines (on two occasions), bursal:body weight ratio, histopathological scoring of bursa of Fabricius and flock performance items such as mortality rate, weight gain, feed conversion rate and production number. Result &Conclusion: In all trials no post vaccine reactions were observed in test and control flocks. Overall, there were no significant differences in response to IBD, ND and AI vaccines between test and control flocks. Immunosuppression indices in both flocks showed no significant differences. All mentioned production parameters were also similar in the test and control groups. Based on IBD titer raised against the vaccine administrated, no interference in generating antibodies versus Newcastle Disease and influenza vaccines, no major lesions in bursa Fabricius in macroscopic and microscopic examination and no side effect in production performance criteria, it is appeared that the vaccine produced by Razi Institute is safe and effective, as the control vaccine, for prevention of IBD. We believe that observation by poultry clinicians in the field confirm the results reported here. In this article details of results obtained from six clinical trials will be presented

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