The gas-phase hydrogenation kinetics of ethylbenzene on Ni/Al2O3 was investigated in a differential microreactor at atmospheric pressure and 130-190 degrees C. Rapid deactivation of the catalyst complicated the steady-state measurements. Reaction orders were near zero for the aromatic compound and between 1.2 (130 degrees C) and 2.3 (190 degrees C) for hydrogen. A rate maximum was observed at 160-175 degrees C, depending on the concentration ratio of the reactants. Mechanistic modelling suggested that the reaction rate is governed by three steps of pairwise sequential addition of hydrogen atoms to adsorbed ethylbenzene. The partially hydrogenated surface intermediates were proposed to have aromatic character. The physical reasonability of the model parameters was discussed.