Situation of Mycoplasma gallisepticum (MG) and Mycoplasma synovae (MS) infections among different chicken flocks in Egypt showed that the infection rates were 100% in commercial broiler flocks, 66% in layers and 40% in broiler parent flocks. Different serological tests, culturing and polymerase chain reaction (PCR) techniques were evaluated for diagnosis of MG and MS. Regarding serological techniques, Haemagglutination inhibition (HI) and ELISA tests proved more specific. The highest number of reactors
were detected by rapid plate agglutination test using stained commercial antigen or liposomal antigen. Detection of MG in yolk sаc of 100 day old chicks by culturing techniques and PCR showed that no cases positive for culture were missed by PCR while 8% of cases were positive for PCR, but negative for culture.