Strain DBF63 utilizes dibenzofuran (DBF) as the sole source of carbon and energy. This strain was identified as a Terrabacter sp. on the basis of the phylogenetic analysis of the sequence of the 16S rRNA gene, in addition to its morphological, biochemical and chemical properties. Two genes encoding extradiol dioxygenases were cloned from strain DBF63 by shot-gun cloning on the basis of the expressed activity of extradiol dioxygenases for 2,3-dihydroxybiphenyl (DHB). One of two clones, E. coli MV1184 (pLM1), exhibited a higher level of activity for DHB than for 3-methylcatechol (3MC), while the other, MV1184 (pKN1) exhibited a low level of activity for both catechol compounds. In addition, the gene carried on pLM1 was lost in strain DBF63W, which is a mutant of strain DBF63 deficient in the ability to utilize DBF and obtained as a result of continuous culture on nutrient broth. These results suggest that the gene (dbfB) carried on pLM1 encodes the extradiol dioxygenase involved in the degradation of DBF in strain DBF63. Nucleotide sequencing of the 8.6-kb KpnI-StuI DNA fragment including dbfB revealed the existence of a hydrolase gene (dbfC), a gene encoding a phenol hydroxylase-like polypeptide, and a region homologous to IS401 of Pseudomonas cepacia ATCC17616. Go-expression in E. coli of dbfBC and carA, the gene products of which catalyze the initial oxidation of DBF to 2,2＇,3-trihydroxybiphenyl (THE), revealed that the products of dbfBC were capable of degrading THE to salicylate. It was also shown that E. coli carrying both carA and dbfBC was capable of degrading dibenzo-p-dioxin (DD).