SUMMARY One thousand serum samples were collected from both culls and normal weight broilers at marketing from 17 different broiler flocks in Ismailia and tested for antibodies against reovirus, infectious bronchitis virus (IBV) and Adeno virus using agar gel precipitation test. Random samples were tested for Mycoplasma gallisepticum (MG) and Mycoplasma synovie (MS) using slide agglutination test. Varying prevalences of both single and mixed infection were evident among both culls and normal-weight broilers. The prevalence of single infection varied from 20%-93.8% for Reovirus with a total of 65%; 26.5-91.8% for IBV with a total of
61.4% and 0%-70% for Adeno virus with a total of 27%. The prevalence of mixed infections was also presented. The highest one was the double infection with Reovirus & IBV (26.8%) followed by the triple infection (18.6%). In contrast, double infections with Reo & Adeno and Adeno & B showed the lowest prevalence (3% and 3.7% respectively). In conclusion, this study showed the wide spread of the three viruses and MG among broiler flocks and its role in increasing culls at marketing was discussed.