few years, we have carefully characterized from a thermody-Apparent and partial molar enthalpies and volumes of aqueous namic point of view the aqueous solutions of homologous solutions of the cationic surfactants 1-(3,3,4,4,5,5,6,6,6-nonafluseries of protiated cationic surfactants, in particular, N-alorohexyl) pyridinium halides and N-octyl pyridinium iodide have kylpyridinium and N-alkylnicotinamide halide surfactants been measured at 298 K as a function of concentration. The (1-3). We have now devoted our attention to the behaviour changes in thermodynamic properties upon micellization have of partially or totally fluorinated cationic surfactants. This been obtained from the experimental data by using a pseudo phase choice is due to both theoretical and practical reasons. In transition approach. The data here reported allow one to evaluate fact, we have already outlined as only a few data about the the effect of the counterion on the energetics of fluorocarbon surthermodynamic behavior of anionic fluorinated surfactant factants solution. This effect, however strong and inversely proportional to the radius of the hydrated counterion, seems to be reduced solutions have appeared in the literature (4, 5). These data with respect to the hydrogenated surfactants, at least as far as were mainly obtained by means of indirect methods, i.e., enthalpic properties of solutions are concerned. In the case of from the dependence of cmc on temperature, pressure, conenthalpies, it qualitatively agrees with that found for the protiated centration of salts, etc.. The data on cationic fluorinated counterparts, but it differs quantitatively. In fact, it is not possible surfactants are completely missing. On the other hand, the to apply directly the group contribution for counterion obtained interest on fluorocarbon based emulsions has been further from the study of protiated analogs. In the case of volume, the increased since they have been proposed and approved as substitution of the counterion simply shifts the absolute scale of the first artificial injectable oxygen-transport fluid for human volume, but does not affect the change in volume upon micellizause (6-9). In order to improve the stability and oxygen tion.