o-Aminophenole was produced through reduction of o-nitroplenole by means of gaseous hydrogen under middle pressure at a temperature of 363 K in an ethanolic Ni-catalyst＇s suspension. The maximum value of the catalyst＇s electrochemical potential (measured by a special combined electrode) was kept at a defined level by controlling the o-nitrophenole feed stream. Under these conditions (＇＇potential controlled hydrogenation＇＇), at ppm-concentrations of the nitro compound, sufficient and stable catalytic activity values of > 100 g amine per g catalyst and hour can be achieved. The o-aminophenole can be isolated very easily by decantation and cooling down the product solution.