An exhaust-gas turbocharger (1) comprising a compressor (2); a turbine (3); and a bearing housing (4), in which there is arranged a bearing cartridge (5), secured against axial displacement and twisting; and a single fixing element (6) securing the bearing cartridge (5) both against axial displacement and also twisting in the bearing housing (4). Also a method for assembling a bearing cartridge (5) in a bearing housing (4) of an exhaust-gas turbocharger (1).