A process for preparing an epoxidation catalyst comprising silver and a high-selectivity dopant on a support, which process comprises depositing a base having a pK.sub.b of at most 3.5 when measured in water at 25.degree. C., on the support prior to depositing silver on the support, and depositing silver and a high-selectivity dopant on the support; the epoxidation catalyst; and a process for preparing an olefin oxide by reacting an olefin with oxygen in the presence of the epoxidation catalyst.