The conformation of sodium bis(2-ethylhexyl)sulphosuccinate (AOT) in CD₃OD, D₂O, CDCl₃, C₆D₆ and a[²H₈] toluene–D₂O microemulsion has been studied using ¹H–¹H and ¹³C–¹H spin–spin coupling constants. In all systems the AOT headgroup exists predominantly in one unequivocally identified conformation with the ester groups gauche to each other, and the sulphite group trans to one ester group. In the ester groups, the conformation of the CH₂—OCO bond is restricted with the carbonyl carbon gauche to both protons. For the OCH₂—CH bond in the alkyl chains there are at least two significantly populated conformations. Secondary splittings in ¹H and ¹³C spectra have been attributed to diastereoisomerism of the alkyl chain asymmetric centres. An error in the previously published assignment of the ¹³C carbonyl spectrum has been corrected. The conclusions of Ueno and coworkers are largely confirmed.