Catalytic hydrogenation of trinitrotoluene over Ni/SiO2, Pd/SiO2 and Pd/C catalysts has been studied in a liquid phase batch reactor at pressure of 2.5 MPA and temperature of 368 K. The surface concentration of atomic hydrogen was estimated by measuring the electrochemical potential of the catalyst and was held on certain different values (potential controlled hydrogenation). In regard of the metal content the activity of Pd-catalysts were higher and related to the catalyst weight the Ni-samples were more active. It has been shown that rapid catalyst deactivation takes place at values below 1% of the equilibrium surface concentration of atomic hydrogen. The observed relation between hydrogenation rate and surface concentration of atomic hydrogen can be discribed by a reaction order of n = - 0.8. This negative order points at a strong influence of hydrogen activation on the rate of trinitrotoluene hydrogenation.