ABSTRACT Mioellization of aqueous mixture of sodium octyl sulfonate ( C8As )/ cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfonate (C12As)( CTAB in the presence of sodium bromide has been studied by surface tension measurement. Nonideal solution theory has been used to calculate the molecular interaction parameters (βM and βs). The oil-aqueous interfacial tensions of C12As/ CTAB, C8As/CTAB, C12As/dodecyl trimethylammonium bromide (DTAB) systems were also measured. We studied the influence of the surfactant concentration, surfactant molar fraction ratio, hydrocarbon chain length, added NaCl and alcohol concentration on the interfacial tension.