A laboratory test was conducted to examine the combined effect of bioaugmentation of an anaerobic bacterial Desulfitobacterium sp. strain Y-51 and addition of zero-valent iron (Fe-0) on the reductive dechlorination of tetrachloroethylene (PCE) in a non-sterile soil slurry. Introduction of a strain Y-51 culture in soil (3 mg vss (volatile suspended solids)/kg soil) containing PCE (at 60 mumol/kg soil) led to complete conversion of PCE to cis-1,2-dichloroethylene (cis-DCE) within 40 d. Treatments of the same soil slurry with Fe-0 (0.1-1.0%) resulted in extended PCE dechlorination to ethylene (ETH) and ethane (ETA). The combined use of a strain Y-51 culture and Fe-0 showed effective dechlorination of PCE than did the, individual use. The cis-DCE produced from biological PCE dechlorination by strain Y-51 was totally converted to non-chlorinated end products by the following chemical reduction by, Fe-0. Furthermore, anaerobic corrosion of Fe-0 was found to stimulate the biological reductive dechlorination of PCE by keeping proper levels of pH and oxidation-reduction potential (ORP) and by producing cathodic hydrogen, which might be used as an electron donor for respiratory PCE dechlorination. These findings suggest that the combined use of bacterial strain Y-51 and Fe-0 is effective for practical treatment of PCE and other chlorinated ethylenes in contaminated sites.