Nanocrystalline　Ni-Cu　alloys　with　a　Cu　content　of　6,　10,　19,　and　32　wt.%　were　prepared　by　pulse　electrodeposition.　The　microstructure　and　tensile　properties　of　the　nanocrystalline　Ni-Cu　alloys　were　characterized　by　x-ray　diffraction,　transmission　electron　microscopy,　and　tensile　testing.　The　x-ray　diffraction　analysis　indicates　that　the　structure　of　the　nanocrystalline　Ni-Cu　alloys　is　a　face-centered　cubic,　single-phase　solid　solution　with　an　average　grain　size　of　18　to　24　nm,　and　that　the　average　grain　size　decreased　with　increasing　Cu　content.　The　ultimate　tensile　strength　(similar　to　1265　to　1640　MPa)　and　elongation　to　failure　(similar　to　5.8　to　8.9%)　of　the　Ni-Cu　alloys　increased　with　increasing　Cu　content.　The　increase　in　tensile　strength　results　from　the　solid　solution　and　fine-grain　strengthening.　Elemental　Cu　addition　results　in　a　decrease　in　stacking　fault　energy,　an　increase　in　work　hardening　rate,　a　delay　in　plasticity　instability,　and　consequently,　a　higher　plasticity.