Ultrasensitive surface-enhanced Raman scattering signals of four typical analytes were observed on Ag nanoparticles from beta-silver vanadate and copper, even though the concentrations of these analytes were as low as 1 x 10(-16) M (Rhodamine 6G or crystal violet) and 1 x 10(-15) M (trinitrotoluene or bovine serum albumin).