High-alloyed stainless steel of 18-8 type and duralumin are not directly weldable due to significant differences in their properties. The results of structural investigations of the joints between the two materials, obtained by a previously developed method of electron beam welding with an Ag-2 wt % Mg alloy filler metal shim, are presented in this paper. The microstructure of the weld is diphasic, being composed of supersaturated Ag in Al solid solution and also an Ag2Al phase. At the base materials and weld boundaries interstitial layers a recrystallized in the form of solid solutions while brittle intermetallic com pounds do not appear. On the basis of presented results a mechanism for the joint formation is proposed.