A modified polyol-based reduction method in ethylene glycol that incorporates poly(N-vinylpyrrolidone) (PVP, M(av) = 10,000; 40,000; 55,000) as polymeric anti-agglomerant alongside a reducing additive (N(2)H(4) x H(2)O, NaBH(4), NaH(2)PO(2) x H(2)O) has been employed to investigate the influence of synthetic parameters on the purity, morphology and stability of an array of polymer-coated copper nanoparticles. While data point to ethylene glycol being capable of acting as a reductant in this system, the use of NaH(2)PO(2) x H(2)O as co-reductant in tandem with the presence of PVP (M(av) 40,000) has rendered nanoparticles with a mean size distribution of 9.6 +/- 1.0 nm that exhibit stability towards oxidation for several months. These data allow us to probe fundamentally how oxidatively stable nano-copper might be achieved.