Amorphous vanadium-niobium mixed oxides with high surface area have been prepared by sol-gel route starting from metal alkoxides using different H2O/V ratios. Dried samples have been characterized by XRD, atomic absorption and BET analysis. Calcination of dried materials up to 550 degreesC in flowing air has been followed with TG-FT-IR spectroscopic analysis. Redox properties of calcined samples have been investigated with TPR technique. Catalytic properties of calcined materials have been tested in the oxidative dehydrogenation of ethane at 550 degreesC and compared with those of a catalyst prepared by impregnation of Nb2O5 with V2O5 having the same composition of gel systems. An improvement of the catalytic performances of vanadium for the gel prepared with the higher H2O/V ratio was found with respect to those of the supported catalyst due to the better interaction between vanadium and niobium.