We have succeeded in rapidly prepg. Ag core-Cu shell nanoparticles (denoted as Cu/Ag nanoparticles) having 10-40 nm in size by a microwave (MW)-assisted alc. redn. process. The core-shell nanoparticles were prepd. by step-by-step successive redn. of a silver precursor and then of a copper precursor added after the formation of silver nanoparticles in 1-heptanol.