This study was conducted on twenty broiler farms located in Beni-Suef and El Minia Governorates during November and December 2009. Fifty birds from each farm were subjected to investigation. Bursae and serum samples were collected. On the basis of lesions of IBD as bursal atrophy, including lymphoid necrosis, stromal edema, and infiltrates of heterophils and macrophages, were first detected in Bursae of Fabricius at 14 days of age and before vaccination. At 37 days, all Bursae of Fabricius had lesions characteristic of IBD, including severe lymphoid depletion, proliferation of epithelial cells, and mild fibroplasia. Although mean maternal antibody levels which estimated by enzyme-linked immunosorbent assay (ELISA)in broilers were apparently protective through day 13, IBD antibodies decreased to non protective levels (below 1,000) by day 15 to 22. Titers began to increase by day 27 to 34 because of field exposure. The prevalence of IBD was 81.5% and 71.1% in Beni-Suef and El Minia respectively. Highest prevalence was found in Beni-Suef and lowest was found in El Mina. The study also showed that the broilers of two weeks of age were subjected to immunosuppression due to bursal damage and suggested that the existing vaccination programs were not effective.