BACKGROUND: Comparison between Infectious Bursal Disease vaccines. OBJECTIVES: Comparison between foreign and Iranian intermediate uncloned Gumboro vaccines on feed conversion ratio. METHODS: Three hundred and thirty day-old chicks were purchased and for determination of vaccination time by Deventer formula, thirty chicks were randomly bled and the remaining chicks divided into 3 equal groups, each group was divided into 4 equal subgroups with the same mean weight. On the basis of Elisa results and vaccine instructions, chicks of group 1 and 2 were vaccinated by uncloned intermediate Gumboro vaccine manufactured by Lohman Company, Germany and Razi Vaccine and Serum Research Institute, Iran subsequently at 16 and 23 days by drinking water. One group was kept as unvaccinated control group. Mean feed intake, weight gains, feed conversion ratio and B:B ratio of 3 groups  were determined at 16, 23 and 42 days. At the end of experiment B:B ratio was measured in 3 groups. RESULTS: This study showed that foreign and Iranian intermediate uncloned Gumboro vaccines had negative effect on mean weight gains and both vaccines atrophied bursa of Fabricius, but had no effect on mean feed intake and feed conversion ratio. CONCLUSIONS: This study showed that foreign and Iranian intermediate uncloned Gumboro vaccines had no effect on feed conversion ratio.