Abstract The intrinsic fluorescence of linear alkylbenzene sulphonate (LAS) has been exploited to show that sodium oleate (Na Ol) and sodium laurate (Na L) comicellize with LAS. It is also shown that comicellization occurs only at concentrations close to the critical micelle concentration (CMC) of Na Ol and Na L. 13C NMR results indicated that in LAS/Na Ol mixed micelles, the oleate molecule loops back and adopts a bent conformation.