A one-pot synthesis of some unsymmetrical 2,5-disubstituted-1,3,4-oxadiazoles via cyclocondensation of benzoylhydrazines with orthoesters under solvent-free and microwave conditions are described here.The reaction is efficiently catalyzed by silicasupported sulfuric acid as it provided the title compounds in high yields and relatively short times.The catalyst is reusable and can be applied several times without considerable decrease in the yields and rates of the reactions.