A cooled current lead for conducting electrical current into a cooled vessel. The current lead comprises an electrical conductor (22) comprising a region (29) which, in use, is heated by electrical current flowing through it; a cooled component (31) situated above a the region (29) and which is provided with a path for removal of heat; and a thermo-siphon comprising a cavity (35) in thermal contact with both the region of the electrical conductor and the cooled component, said cavity containing a fluid (35).