The surfactant Cu(AOT)(2) forms reverse micelles when dissolved in cyclohexane. In this study the dynamics of the Cu2+ ion in such aggregates was studied using the ESR technique by studying the shape and the line width of the Cu2+ ESR spectrum as a function of surfactant concentration and water content. In order to obtain a more detailed picture, we diluted the Cu(AOT)(2) magnetically (with Zn or Na). Two different sites were observed with different mobilities and most likely with different symmetries. One site, which is present at low water content, has a Cu(II) ion bound to one or two sulfonate head groups. The other site, which is present at high water contents, is the hexaaquocopper(II) ion, and in this site, the Cu(II) ion shows a high mobility.