Effects of alloying on mechanical properties of solidification processed polycrystalline MoSi 2 , ternary (Mo, 2.5 at.% Re)Si 2 , Mo(2 at.% Al, Si) 2 , (Mo, 1 at.% Nb)Si 2 , and quaternary (Mo, 1 at.% Re)( 2 at.% Al, Si) 2 alloys were evaluated by microhardness testing at room temperature and compression testing at elevated temperatures. Alloying with 2.5 at.% Re resulted in an anomalously high solid solution hardening in MoSi 2 , while alloying with 2 at.% Al lowered the brittle-to-ductile transition temperature, in compression, of polycrystalline MoSi 2 from 900 o C to =<25 o C. Similar to the effects observed in the quaternary (Mo, 1 at.% Re)(2 at.% Al, Si) 2 alloy, 1 at.% Nb containing samples exhibited concurrent enhanced ambient temperature ductility and higher elevated temperature strength compared to pure MoSi 2 . The effects of alloying MoSi 2 with 2.5 at.% Re, 1 at.% Re+2 at.% Al, and 1 at.% Nb on hardness and yield strength are discussed.