Acute respiratory tract infections are of paramount importance in the poultry industry. In Respiratory diseases, involvement of Newcastle disease virus (NDV), Infectious bronchitis virus (IBV), Mycoplasma gallisepticum (MG) and Escherichia coli (E.coli) can be suspected. Most of these usually occur as complex, some being primary while others complicating the situation as secondary pathogens. Broilers have been observed mostly affected with respiratory as complex respiratory disease (CRD), leading to high mortality and huge conomic losses. The results showed that 13% and 14.8% were infected with NDV and IBV respectively, whereas 5.2, 6.0, 9.6, 10.4 and 11.3%  were infected with both NDV and MG, IBV and NDV, IBV and MG, NDV and E.coli and IBV and E.coli respectively. Furthermore, 2.6% were infected with IBV, NDV and MG, also 15.7% were infected with IBV, NDV, MG and E.coli at the same time: On the other hand 11.3% of the serum samples examined were negative for the above-mentioned respiratory diseases