In this study, the effect of hydrogen in argon as shielding gas was investigated for tungsten inert gas welding of 316L austenitic stainless steel. The microstructure, penetration and mechanical properties were examined. Pure argon, 1.5%H-2-Ar and 5%H-2-Ar were used as shielding gas. The highest tensile strength was obtained from the sample which was welded under shielding gas of 1.5%H-2-Ar. After bending test, cracks, tearing and surface defection were not observed on the samples that were welded under all three shielding media. Mean grain size in the weld metal increased with increasing hydrogen content. Additionally, weld metal penetration depth and its width increased with increasing hydrogen content. (C) 2003 Elsevier Ltd. All rights reserved.