The damage to human hair caused by permanent waving treatment was examined from the viewpoint of structure with several spectroscopic methods, C-13 CP/MAS n.m.r., wide angle X-ray diffraction (WAXD), FTi.r. and Raman methods. The partial disruption of alpha-helical structure constituting the microfibril in hair fibre was revealed by this study, although the incomplete re-oxidation of the disulphide bond has been considered to be the main damage caused by the treatment. Moreover, this disruption was mainly caused in the first reduction process. In particular, C-13 CP/MAS n.m.r. gave the quantitative evaluation for change of alpha-helical content in the microfibril with permanent waving treatment. In addition, FTi.r. and Raman spectra indicated that the alpha-helix was partially changed to random coil, rather than to beta-sheet structure.