The results of experimental studies of the erosion rate of high-purity tungsten cathodes after pulsed arc discharges in a pure oil-free ultrahigh vacuum and in gases of various purities are reported. The erosion rate in high-purity argon does not change compared to the rate of erosion of electrodes in a pure oil-free vacuum. The rate of erosion in "technical" argon is 10% less than the rate of erosion of electrodes in an oil-free vacuum. The rate of erosion in "technical" nitrogen is 15-35% less than the rate of erosion of electrodes in vacuum. Particle sizes formed in gas arcs are smaller than those formed in vacuum arcs.