ABSTRACTA brief review will be given of the preparation, synthesis and properties of the Cu/Co system. The special case of the synthesis of nanocrystalline Cu.80Co.20 by precipitation and reduction of hydroxides is discussed in more detail. It was found that the lattice constant of nanocrystalline Cu.80Co.20. determined from x-ray diffraction measurements, approximately fits Vegard's Law and the average nearest neighbor distance from both the Cu and Co atoms, determined from EXAFS measurements, ir shifted from their bulk values. Samples given the minimum heat treatment needed to reduce the hydroxides contained Co-rich regions. Heat treatments cause the Co to segregate preferentially onto the surface of the Cu crystals. The presence of the Co delays the oxidation of the Cu surfaces.