In the present study, Ni incorporated MCM-41 structured mesoporous catalysts with a Ni/Si atomic ratio of 0.036 and 0.15 were prepared by a direct hydrothermal synthesis procedure. These catalysts had surface area values of 860.5 m(2)/g (Ni-MCM-41 having a Ni/Si ratio of 0.036) and 944.9 m(2)/g (Ni-MCM-41 having a Ni/Si ratio of 0.15). They also had narrow pore size distributions with average pore diameters of 2.7-2.6 nm respectively. Ni MCM-41 synthesized by the one-pot hydrothermal synthesis procedure showed very high activity and relatively high hydrogen yield in steam reforming of ethanol in a temperature range between 300-550 degrees C. Besides the steam reforming reaction, formation of some formaldehyde and small amounts of ethylene were also observed at low temperatures for the catalyst containing a Ni/Si ratio of 0.036. The disappearance of formaldehyde and the formation of some methane at high temperatures indicated the increased significance of cracking in addition to reforming and dehydration reactions. The increase of the Ni/Si ratio makes the catalyst more active at lower temperatures.