Catalytic hydrodechlorination via Pd catalysts is an efficient way to destroy chlorinated hydrocarbon compounds (CHCs) in aqueous systems. However, its application in groundwater suffers from rapid catalyst deactivation, e.g. by sulfur poisoning and interference with biological processes, such as growth of sulfate-reducing bacteria. In this paper we describe the application of a tailored catalyst for groundwater remediation in a full-scale field installation. The catalyst (I'd on a hydrophobic zeolite Y) was operated in a flow-through mode over 2 years and showed sustained removal efficiencies. Typical half-lives for CHC reduction were between 1.5 and 3 min. As the addition of the reductant hydrogen results in favorable conditions for sulfate-reducing bacteria, the system was periodically flushed with a dilute H2O2 solution to prevent the growth of this type of bacteria. With this it could be shown, that a catalytic method with noble metals for the direct reductive destruction of chlorinated contaminants in groundwater can be operated over extended periods of time with sustained efficiencies. (C) 2004 Elsevier B.V. All rights reserved.