Abstract The radical anion of tetracyanoethylene (TCNE), when produced in the presence of the macrocyclic polyether dibenzo-18-crown-6, was found to be a convenient spin probe for studying amphiphilic liquid crystals. Both the value of the isotropic nitrogen hyperfine splitting constant and the broadening induced on the ESR lines by the addition of the paramagnetic salt NiC12 to the lyotropic mixture, seem to indicate that TCNE resides in the polar interfacial region of the liquid crystal.