The dependence of limiting amounts of solubilized water upon the concentration of sodium 1,2-bis(2-ethylhexyloxycarbonyl)ethanesulfonate (AOT) in apolar solvents was measured by the Karl-Fischer method at 30-degrees-C. In the solubilization regions, two or three states of water, i.e., water bound directly to ionic head groups of AOT and water bound to the hydrated ionic groups or bulk-like water, were found to exist from NMR, ESR, fluorescence, and near infrared spectroscopic measurements. These types of water were related to the formation of reversed and swollen micelles or W/O microemulsions.