In order to enhance benzothiophene (BT) degradation, a flavin-oxidoreductase gene, dsz D from dibenzothiophene (DBT) desulphurizing Rhodococcus erythropolis KA2-5-1 was expressed in BT desulphurizing Rhodococcus sp. strain T09 using a Rhodococcus-E. coli shuttle vector. The BT degradation rate was increased about threefold with BT grown recombinant cell, suggesting that the flavin-oxidoreductase is involved in BT degradation and the dsz D gene product could replace its native oxidoreductase, although Western blotting analysis revealed the strain T09 flavin-oxidoreductase was immunologically different. The dsz D gene product was expressed even when inorganic sulphate was used as the sole sulphur source.