The structure and mechanical properties of ternary Mg-(Sc, Ag)-X (X= Al, Ca, Zn, Y, Mn, Sn and Si) rapidly solidified (RS) ribbons were investigated. Alloy compositions having the best-combined properties of ductility and hardness (> WHO) were a Mg97Sc1Y2 alloy in Mg-Sc-X system and a Mg96.5Ag0.5Y3 alloy in Mg-Ag-X system. It is expected that the RS powder metallurgy alloys having a high yield strength above 600 MPa and an elongation above 5 % can be developed in the Mg97Sc1Y2 and Mg96.5Ag0.5Y3 compositions.