Background and Aims: Infectious bronchitis virus (IBV) causes an acute, highly contagious respiratory and kidney disease of chickens which results in significant economic losses in commercial broilers, layers and breeders. Rapid identification of IBV serotypes involved in respiratory complex is a problem in the differential diagnosis.

Materials and Methods: In this study, a single and multiplex RT-PCR was used to detect group III, Massachusetts and 793/B serotypes of IBV that have been circulating in Iranian poultry industry since 1999.

Results: Only seven out of 49 allantoic fluid samples showed positive results in single RT-PCR using group specific primers. Two of these samples belonged to IBV positive group in VN test. Whereas four samples belonged to H9N2 positive group and one sample belonged to IBV/AIV negative groups. The high sensitivity of single RT-PCR led to detect some of the missed IBV infections as compared with other virological tests. Three out of 7, IBV isolates identified with single RT-PCR, classified as 793/B serotype and four of them categorized as Massachusetts serotype in multiplex RT-PCR.