The rate of production and the composition of fume from the use of coated electrodes for filler material in electric arc welding were studied in relation to the hygienic significance of the fume. When a limit of 10 mg/m3 was applied for total fume, manganese oxides were found to be controlled, but in some instances compounds of fluorine were not adequately controlled. A system for classification of coated electrodes relative to their potential health hazards is proposed.