Control of the size of metallic copper particles formed in reverse micelles of AOT (sodium bis(2-ethylhexyl)sulfosuccinate) was achieved by varying water content, reagent concentration, and intermicellar interactions. In the 1-12 nm range, the size of metallic copper particles can be deduced from the measure of the optical densities at two wavelengths. It has been demonstrated that the size of the metallic copper particle depends upon the number of copper ions and reducing agents per micelle. In particular, it was observed that decreasing intermicellar attractions decrease the crystallite size.