The oxidative dehydrogenations of ethane and propane were investigated over a series of zirconia and nickel-oxide supported on zirconia catalysts. It was found that zirconia, sulfated zirconia as well as NiO-based zirconia catalysts showed high catalytic activities for oxidative dehydrogenation of ethane and propane. However, conversion and selectivity differed depending on the nature of the catalysts. Zirconia, sulfated zirconia (SZ) and their supported NiO catalysts showed high ethane conversions but lesser selectivities to olefins while NiO/Li2ZrO3 exhibited high selectivities to ethylene and propylene. Addition of an LiCl promoter in the NiO/SZ catalyst increased the catalytic activity and olefin selectivity, thus resulting in a higher olefin yield. In the oxidative dehydrogenations of ethane and propane NiO-LiCl/SZ exhibited 79% ethylene selectivity at 93% ethane conversion at 650 degreesC and 52% selectivity to propylene at 20% propane conversion at 600 degreesC, respectively. Characterization showed that the physico-chemical properties of the catalysts determine the catalytic activity and selectivity.