This paper deals with infectious bronchitis as one of the most important diseases in chickens, which causes great economic losses. Infectious bronchitis is caused by avian coronavirus, which is found worldwide. Infections, depending on the strain, may cause an acute upper-respiratory tract disease, drop in egg production, decreased in egg quality, and nephritis. Conventional and more advanced methods have been used for the diagnosis of IBV infection. The choice on one test over another is guided by type of sample, availability of the test materials and facilities, test reporting time, purpouse of the test, and whether the test is carried out in the field or at the laboratory. In the past, serological assays such as virus neutralisation (VN) and haemagglutination inhibition (HI) were used widely for detecting and serotyping of IBV strains. Today ELISA is most frequently used for serology, and molecular methods for virus detection and typing. The main approuch to control of IB is by the use of live and killed vaccines. Generally, the available live and killed vaccines provide a very good protection against IB, only if they are delivered accurately so that each bird received a full dose. While the current vaccines are generally very satisfactory, several laboratories have worked on the development of new generation vaccines. These have been designed by molecular methods, most of which are intended to enable vaccines to be tailored to particular local requirements.