Copper oxide-zinc oxide catalysts are used for commercial production of hydrogen through water gas shift (WGS) reaction in the temperature range of 440-523 K. It is observed thai, unsupported metallic copper does not show high activity and both the activity and stability increase by supporting the active component as copper oxide on other oxides such as zinc or chromium oxide. These catalysts have been characterised by various surface techniques as well as WGS activity. It has been shown that the mechanism of WGS reaction depends upon the type of support used. It is proposed that in case of copper-zinc oxide catalyst the WGS reaction involves both Eley Rideal and redox mechanism whereas for copper chromium oxide catalyst the mechanism is purely redox type due to weak Cu-O bonding.