 - As halogenated waste is xenobiotic with no analogous compounds in nature, there is no natural means of ameliorating the negative environmental impact caused by halo-organic emissions. The presence of organo-halogens in effluent discharges is of increasing concern, owing to the mounting evidence of adverse stratospheric ozone, ecological effects, and the impact on public health. There is a pressing need, driven by legislative and financial imperatives, to develop robust and efficient treatment technologies. This Review considers the application of catalytic hydrodechlorination (HDC) as a progressive approach to the conversion and recycling of toxic chloro-compounds. An overview of the existing treatment technologies is provided with an assessment of the benefits of catalytic HDC over separation/oxidation methodologies. Taking the transformation of chloro-aromatics, the catalytic HDC of liquid and gas phase reactants is considered in turn with a critical analysis of the pertinent literature. Two "case studies" are considered in detail: i) the liquid phase HDC of chlorophenols over alumina supported palladium, focusing on the critical process and catalyst structural characteristics that influence HDC performance; ii) the gas phase conversion of a range of halogenated (Cl and Br) aromatics over silica supported nickel with an examination of the dehalogenation activity/selectivity response as a function of the nature of the aromatic reactant. 