The mechanical properties of Al-(Mg)-0.5Sc alloys have been investigated. Room-temperature tensile and toughness properties were found to reflect a superposition of the properties of Al-Mg and Al-0.5Sc alloys and are quite competitive with high-performance Al alloys. A combination of substructure refinement by Mg and stabilization by Al3Sc precipitates produces exceptional superplasticity as exemplified by superplastic forming (SPF) elongations in excess of 1000 pct at a strain rate of 0.01 s-1. Overall, these alloys demonstrate an extremely attractive combination of strength, toughness, density, and SPF fabricability. © 1990 The Minerals, Metals & Materials Society - ASM International - The Materials Information Society.