The present invention if for a catalyst for epoxidation of an alkene, such as ethylene, to an alkene oxide, such as ethylene oxide, on which silver has been deposited on alumina as a support which has been modified with certain weak base compounds, such as oxides of a Group 1A, Group 2A, Group 3A or the first transition series of the Periodic Table of Elements, and with a high temperature heat treatment. Optional promoters selected from the group consisting of compounds of Group 1A, Group 2A, Group 7A and Group 8 may be contacted with the alpha-alumina support in solution with a silver compound, with the catalyst precursor before calcination or with the catalyst after calcination. The catalyst is brought into contact with alkene and oxygen under reaction conditions to selectively convert the alkene to an alkene oxide.