A discharge lamp with excellent arc stability and excellent durability in which the use level of thoriated tungsten is restrained has an anode and a cathode in the interior of a discharge vessel, wherein said cathode is made up from a thoriated tungsten part with a tungsten filling ratio of at least 90 vol.-% and a main body part connected to said thoriated tungsten part and consisting of pure tungsten, wherein a ratio ST/S of a side surface area ST of said thoriated tungsten part and a side surface area S of said cathode is in a range of from 0.005 to 0.15, with the proviso that, in case the cathode has a length in the direction of the cathode axis which exceeds twice the maximum diameter of the cathode, a side surface area S is used for calculating the ratio ST/S which corresponds to the side surface area where the distance along the cathode axis from a tip end adjacent to the anode is twice the maximum diameter of the cathode.