Synchrotron radiation small-angle x-ray scattering (SAXS) and phase behavior investigations were combined to study the effect of compressed CO2 on the stability and structure of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles in isooctane at different temperatures, CO2 pressures, AOT concentrations, and the molar ratios of water to surfactant w ([H2O]/[AOT]). SAXS measurements indicate that the size of the reverse micelles depends markedly on the pressure of CO2 and w. Increasing pressure of CO2 results in reduction of the micellar size. The effect of CO2 pressure on the size and structure of the reverse micelles is nearly independent of the concentration of the surfactant. The results of SAXS also give the information about the stability of the reverse micelles, which agrees with that obtained from the phase behavior investigation. (C) 2003 American Institute of Physics.