The thermal stability and glass forming ability of Cu(50-x)Zr(43)Al7Ag(x) (x=0, 1, 3, 5, and 7) bulk metallic glass alloys have been investigated. The glass forming ability in the Cu-Zr-Al-Ag alloys increased proportionally to the Ag content and show good correlations with thermal parameters such as ΔT(x)(=T(x)-T(g)), T(rg)(=T(g)/T(1)) and γ(=T(x)/(T(g)+T(1))). For the Cu(43)Zr(43)Al(7)Ag(7) alloy, fully amorphous rods of 8 mm diameter were successfully fabricated by copper mold casting. Mechanical tests on this composition revealed also remarkable properties with compressive strength around 2000 MPa and large ductility.