In the present paper, we investigate in deeper detail some features of the bistable behavior observed in micellar aggregates of gangliosides. In these systems, a collective transition takes place connected to different possible conformations of the glycosidic headgroup and resulting in different aggregation numbers for different thermal hystories. Light scattering experiments per-formed on mixed micelles indicate that it is the aggregated structure which dictates the conformation a ganglioside monomer assumes, among the allowed ones. Moreover, density measurements confirm the results previously obtained by DSC and show that the conformation of the hydrophobic tails at a given temperature is coupled to that of the headgroup. NMR measurements are consistent with previous results and, on a more local scale, indicate that the hydration of the ganglioside molecule is affected by the conformational transition. (C) 2002 Elsevier Science B.V. All rights reserved.