The micellization characteristics of N-cetyl-N-ethanolyl-N,N-dimethyl and N-cetyl-N,N-diethanolyl-N-methyl ammonium bromides have been investigated by microcalorimetric, conductometric, and fluorimetric techniques. The critical micellar concentration (cmc), counterion binding of micelles, their aggregation number, and thermodynamics of micellization have been evaluated at eight different temperatures in the range of 288-323 K. The Gibbs free energy, enthalpy, entropy, and specific heat of the micellization process have been evaluated by the direct calorimetric method as well as by the indirect method of van't Hoff by processing the cmc results of micro calorimetry and conductometry at different temperatures. The differences of the results obtained by these two procedures have been discussed. The thermodynamic results have been compared with values for the parent compound, N-cetyl-N,N,N-trimethylammonium bromide, and the effect of the substitution of the ethanolyl group in place of the methyl group on the surfactant head has been rationalized. The effects of the salt NaBr on the thermodynamics of micellization of the studied surfactants have been also studied from the microcalorimetric measurements.