An experiment was designed to test the hypothesis that bioremediation within DNAPL source zones is feasible provided all limiting factors are delivered in adequate amounts. A demonstration-scale aboveground aquifer simulation system was bioaugmented with a mixed anaerobic dechlorinating culture after the addition of neat PCE below the water table. Hydrogen Releasing Compound RTM was introduced to the tank to provide a long-term and steady supply of reducing equivalents for dechlorination. The system effluent was monitored for chlorinated ethene concentrations, and results demonstrated the dechlorination of PCE to trichloroethene (TCE) and cis-dichloroethene (cis-DCE). Measurements at the end of the study indicated the following mole fractions in the effluent: cis-DCE (66%), TCE (24%), and PCE (10%).