The homology among the genes coding for degradation of bipheny(BP) and 4-chlorobiphenyl(4CB) was comparatively analyzed by Southern hybridization in several BP/4CB degrading bacterial strains. As the hybridization results of their genomic DNAs with pcbABCD as the DNA probe, the group of Pseudomonas sp. DJ-12. P08 and P27 strain was separated by the group of P20 and P1242 strains. The P. pseudoalcaligenes KF707 showed the hybidization signal which was homologous to the group of DJ-12, but they had different restriction endonuclease sites. The pcbAB genes in pCUl recombinant plasmid from Pseudomonas sp. DJ-12 appeared to be homologous to pchAB genes in pKTF20 cloned from P. pseudoalcaligenes KF707, but the C genes in both strains were not homologous. The bphABC in pKTF20 showed the signals homologous to the cbp ACB in pAW6194 cloned from P. putida OU83, but homologous signal was not found botween the pcbABCD genes in pCUl and the cbpADCB genes in pAW6194 recombbinant plasmid.