Three omega-hydroxyalkyldodecyldimethylammonium bromide surfactants, referred to as 12-mOH, with m = 6, 8, and 12, have been synthesized and their critical micelle concentration, micelle ionization degree, and aggregation numbers have been investigated by means of electrical conductivity, spectrofluorometry, and time-resolved fluorescence quenching. Contrary to the corresponding alkyldodecyldimethylammonium bromide surfactants (referred to as 12-m) which show extensive micellar growth at relatively low surfactant concentrations (P. Lianos, J. Lang, and R. Zana, J. Colloid Interface Sci. 91, 276, 1983), the 12-60H and 12-80H surfactant micelles remain small and probably spherical up to relatively high concentrations. This striking difference in behavior reflects the fact that the alkyl chain of the 12-m surfactants is part of the micelle hydrophobic core whereas the omega-hydroxyalkyl group remains in contact with water as part of the surfactant head group. The 12-120H homologue is soluble only at temperatures above 40 degrees C and forms small micelles at 55 degrees C. When its micellar solutions are cooled below the clarification temperature slightly bluish systems are obtained, probably revealing the presence of vesicles.