An experimental investigation in gas tungsten arc welding with the hydrogen addition to argon was made. The hydrogen addition to argon makes the arc constrict and the energy concentrate in the arc, which produces increase in arc power. Experimental welding was carried out on three base metals, i.e., low-alloy steel, high-alloy stainless steel, and an aluminum alloy, using no filler material and in argon with the addition of 0.5-20% hydrogen. In welding of stainless steel with the addition of 20% hydrogen to argon, the quantity of the base metal melted increases by three to five times, with the other parameters remaining the same, in welding of low-alloy steel by three times, and in welding of aluminum by six to nine times. The experimentally obtained results were compared with the theoretical ones. With both steels, the experimental and theoretical results agreed well, but with aluminum, they differed very much.