Diagnosis of the DE072 strain of infectious bronchitis virus (IBV) by the reverse transcriptase-polymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP) serotype identification test was not possible because the primer used in the RT-PCR did not amplify the S1 gene of the DE072 strain. The 3' end of the polymerase gene and the 5' end of the S2 gene of the DE072 strain were sequenced and compared with the forward and reverse RT-PCR primers, respectively. A 2-bp mismatch at the 3' end of the reverse primer was found. On the basis of these data, a degenerate primer that could amplify the S1 gene of the DE072 strain as well as eight other serotypes of the virus was synthesized. In addition, we were able to differentiate the DE072 strain from all of the other IBV strains examined by RFLP analysis of the RT-PCR product.