When [U-^(14)C] 3. 3`, 4, 4`-tetrachloroazobenzene([U-^(14)C] TCAB) was added to the MM₂medium as a sole carbon source for the isolated microorganisms and incubated, some radioactive metabolites were detected by autoradiography. No ^(14)CO₂ was evolved from [U-^(14)C] TCAB which was added as a sole carbon source to an organic matter-free soil inoculated by the isolates, wetted with the MM₂ salt medium, and incubated at 30℃. One of the metabolites in pure culture of Achromobacter group VD, which was isolated and identified, was tentatively identified as a compound of m/z 250 by means of GC/MS. The possible pathways for its formation are thought to include dechlorination from the TCAB structure, hydroxylation, ortho fission of the two benzene rings, and reduction of the resulting carboxyl group.