An ethylene oxide catalyst consists of silver deposited on an alumina carrier. It has been treated to with an aqueous basic salt solution, the pH of the aqueous treating solution is maintained above 8 during the treatment. An ethylene oxide catalyst is provided which is essentially transition metal and rhenium free and which consists essentially of silver, alkali metal, sulfur and boron components on a support such as alumina, optionally with fluorine or chlorine component.