A method for the start-up of a process for the epoxidation of an olefin, which method comprises contacting a catalyst bed comprising a silver-based highly selective epoxidation catalyst, or a precursor of the catalyst comprising the silver in cationic form, with a feed comprising oxygen at a temperature of the catalyst bed above 260.degree. C. for a period of at most 150 hours, and subsequently decreasing the temperature of the catalyst bed to a value of at most 260.degree. C., and a process for the epoxidation of an olefin, which process, comprises contacting a catalyst bed comprising a silver-based highly selective epoxidation catalyst, or a precursor of the catalyst comprising the silver in cationic form, with a feed comprising oxygen at a temperature of the catalyst bed above 260.degree. C. for a period of at most 150 hours, and subsequently decreasing the-temperature of the catalyst bed to a value of at most 260.degree. C. and contacting the catalyst with the feed comprising the olefin and oxygen.