A beneficial effect of alloying with Sc and Zr on microstructure and mechanical properties of highly alloyed Al-Zn-Mg-Cu alloys with an increased content of Zn (to 10-12%(1)) was investigated. The alloys were produced by casting with a cooling rate of 50 degreesC/s and then extruded to rods at 400 degreesC. Tensile properties of the rods in T6 condition are discussed in connection with the results of microstructural investigations. It is shown that alloying with Sc and Zr permits the UTS to be achieved as high as about 820 MPa at ductility level of 5.8% (in the alloy containing 12% Zn).