The effect of primary, linear alcohols (ethanol to hexanol) on the micellar properties (CMC, micelle ionization degree β and molecular weight M w composition of the mixed alcohol + surfactant micelles) of solutions of alkyltrimethylammonium bromides (octyl to hexadecyl) has been investigated, with particular emphasis on the system pentanol-tetradecyltrimethylammonium bromide (TTAB). The studies involved measurements of conductivity and bromide ion activity (CMC, β); light scattering (CMC, M w at CMC); osmometry ( M w); decay of fluorescence of micelle-solubilized pyrene (surfactant aggregation numbers for the mixed alcohol + surfactant micelles at given alcohol and surfactant concentrations); and solubilization of alcohols in micellar solutions (mixed micelle composition). The results show that the addition of alcohol decreases the CMC and M w at CMC and increases β at CMC. Moreover, the micelle molecular weight at a given alcohol concentration always increases with the surfactant concentration. Striking differences have been found in the changes of M w of TTAB micelles in H 2O-pentanol mixtures in the presence of 0.1 M KBr and in the absence of salt. These various results have been explained in terms of the effect of the micelle-solubilized alcohol on the micelle surface charge density, and on the dielectric constant of the micelle palisade layer. The change of the standard chemical potential of the micellized surfactant with the micelle composition provides an explanation for the changes of the surfactant aggregation number with the surfactant and alcohol concentrations, and with the nature of the added alcohol. Some results suggest that butanol and longer alcohols may affect the micelle hydrophobic core, whereas propanol is too short to do so.