The efficiency of removing trichloroethylene (TCE) using co-immobilized zero-valent iron and autotrophic hydrogen-bacteria has been studied in this research. Laboratory results show that the combined physicochemical and biological system is much superior to either physicochemical or biological system alone in dechlorination of TCE. In addition to catalyzed hydrogenolysis reactions occurring between hydrogen gas and zero-valent iron particle surface, as well as autotrophic dechlorination of hydrogen-bacteria, the FeS produced by sulfate-reducing bacteria also contributes to the catalytic dechlorination mechanisms. In the presence of hydrogen gas, corrosion of iron powder is somewhat alleviated, thus extending the useful life of iron powder for treating pollution. The results of membrane feeding substrate bioreactor (MFSB) reveal that the TCE removal rate of the combined system is 3.5 times faster than the zero-valent iron method, and 5 times faster than the biological treatment method in removing TCE. The potential of using co-immobilized zero-valent iron and autotrophic hydrogen-bacteria to clean up sites contaminated by chlorinated hydrocarbons is demonstrated by the results presented in this paper. (C) 2008, The Society for Biotechnology, Japan. All rights reserved.