The reweldability of austenitic alloys has been studied for flat specimens of Cr16NillMo3Ti (Russian) and 316L(N)-SPH (European Union) which have been implanted with helium using cyclotron facilities. Specimens with typical thicknesses of 1 mm have been implanted up to helium concentrations of 50, 100, 300 and 860 appm on both sides. Electron beam welding of Cr16NillMo3Ti resulted in weld cracking for specimens with the highest helium concentration of 860 appm, unlike the 316L-SPH material in similar conditions. A reduction in fatigue life in low cycle fatigue was found to be more significant for welded joints of Cr16NillMo3Ti material.