Gold and gold-copper particles of sizes of the order of nanometers were prepared in reverse micelles, with different sizes of the water pool, by controlled chemical reduction of metal cations. The nanoclusters were characterized by a combination of dynamic light scattering (QELS), transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The results indicate that it is possible to obtain a uniform or nearly uniform particle size distribution and that compound metallic nanparticles of Cu3Au can be prepared by this method. At present we have no evidence on the mechanism that lead to mixing at the atomic level; nevertheless, it appears possible to exploit the method in order to prepare mixed bimetallic phases of various composition.