Electrical conductivity, spectrofluormetry, and self-diffusion measurements have been used to provide evidence for, and study of , binding of ions (Na+, Cl-) to the micelles of a series of zwitterionic surfactants of the alkanediyl-alpha-(dodecyldimethylammonio)-omega-carboxylate type with the intercharge alkanediyl group being CH2, C3H6, C5H10, and C10H20 (referred to as C12N1CO2, C12N3CO2, C12N5CO2, and C12N10CO2, respectively). These surfactants permitted us to assess the effect of the carbon number of the intercharge group on the binding of Na+ and Cl- to the zwitterionic micelles. The propanediyl-1-(dodecyldimethyl-ammonio)-3-sulfonate (C12N3SO3) has also been investigated to check the effect of the headgroup. In most experiments, the molar concentration ratio [surfactant]/[salt] was kept constant and equal to 1. The degrees of ion binding have been obtained for both Na+ and Cl- as a function of the surfactant concentration, from self-diffusion measurements. The degree of binding is always larger for the anion and follows the sequence C12N1CO2 < C12N3SO3 < C12N3SO2 < C12N5CO2 approximate to C12N10CO2, both for Na+ and Cl-. The ions by zwitterionic micelles starts only well above the cmc and increases rapidly with concentration. A mass action model has been developed and provides a quantitative account of the results.