Abstract: This invention relates to a supported silver catalyst for the manufacture of ethylene oxide which contains a combination of (a) cesium and (b) at least one other alkali metal selected from the group consisting of lithium, sodium, potassium and rubidium, which combination comprises (a) and (b) in amounts in relation to the amount of silver therein sufficient to increase the efficiency of ethylene oxide manufacture to a value greater than the efficiencies obtainable under common conditions from respective catalysts which are the same as said catalyst except that instead of containing both (a) and (b), one contains the respective amount of (a), and the other contains the respective amount of (b). There is also described herein a process of making such catalyst and a process for producing ethylene oxide with such catalyst.