The pathogenicity of a recent isolate of Infectious bursal disease virus (IBDV), IR499, isolated from a nonvaccinated flock with 17.5 % mortality rate in susceptible SPF chickens, chickens embryos and broilers was discussed. The molecular characterization of the virus based on the restriction fragment length polymorphism (RFLP) pattern was also investigated. The mortality rates were 85% and 22% in SPF and broiler chickens, respectively. The bursal weight indexes were 4.7 and 1.2 for SPF birds and 1.7 and 0.7 for susceptible broilers four and nine days post inoculation, respectively. The gross lesions were generalized including moderate to sever bursal hemorrhage. Using RT-PCR, a 643bp PCR product was amplified then nested PCR was carried out to amplify a 552bp PCR product. The 552bp product was subjected to SspI, StuI, HhaI and SacI restriction enzymes digestion which was SspI and StuI double positive and HhaI and SacI double negative. The pathogenicity and RFLP pattern finding confirmed that the IR499 virus could be classified as a very virulent IBDV.