The secondary structure alterations, accompanying isothermal and temperature guided beta-casein micellization have been studied by dynamic light scattering, circular dichroism and Fourier transform infrared spectroscopy techniques. Micelle formation induced by increase of protein concentration at constant temperature is accompanied by the formation of scanty number of additional peptide hydrogen bonds, preliminary assigned to intraprotein beta-structure. Heating results in more pronounced but qualitatively different changes consisted in dehydration of peptide groups and disruption of polyproline II helix segments with subsequent conversion to random and beta-turns. Nevertheless, in both cases the total number of residues involved in transition is quite few and cannot be regarded as a decisive factor for casein micellization.