We have observed the temperature stability of the amorphous structure in many transition‐metal‐alloy systems (Nb‐Mo, Ta‐W, Nb‐Zr, Mo‐Ru, W‐Re, Mo‐Rh, Ta‐Re, Zr‐Mo, Ta‐Ir, and Zr‐Ru) prepared by electron‐beam evaporation onto liquid‐helium‐cooled substrates. Past observations which established criteria for the formation of amorphous metallic alloys were largely limited to close‐packed elements. In this paper, which includes a large number of bcc elements, we find that the crystalline‐state immiscibiltiy of the elements is a stronger factor in determining the stability, as well as the ease of formation of the amporhous structure, than is the difference in atomic size of the constituent elements.