A catalyst which comprises a carrier and silver deposited on the carrier, which carrier has a surface area of at least 1 m2/g, and a pore size distribution such that pores with diameters in the range of from 0.2 to 10 μm represent at least 70% of the total pore volume and such pores together provide a pore volume of at least 0.27 ml/g, relative to the weight of the carrier; a process for the preparation of a catalyst which process comprises depositing silver on a carrier, wherein the carrier has been obtained by a method which comprises forming a mixture comprising: a) from 50 to 90% w of a first particulate α-alumina having an average particle size (d50) of from more than 10 up to 100 μm; and b) from 10 to 50% w of a second particulate α-alumina having an average particle size (d50) of from 1 to 10 μm; % w being based on the total weight of α-alumina in the mixture; and shaping the mixture into formed bodies and firing the formed bodies to form the carrier, and a process for the epoxidation of an olefin, which process comprises reacting an olefin with oxygen in the presence of a said catalyst.