The first 440 nucleotides of the S1 part of the spike protein (S) gene of three nephropathogenic infection bronchitis virus (IBV) strains (BJ1, BJ2 and BJ3), isolated from three rural chicken farms of Beijing with outbreaks of avian infectious bronchitis, were sequenced after reverse transcriptasenested polymerase chain reaction amplification. The sequence data were analyzed and compared with the standard IBV strains M41, Beaudette, vaccine strain H120 and Chinese vaccine strain D41. The three IBV isolates and strain M41 showed more than 99.1 and 97.8% identity in nucleotide sequence and deduced amino acid sequence, respectively, suggesting that the three nephropathogenic IBV strains belonged to the Massachusetts genotype of IBV.