For the purpose of improving the properties of keratin fibers by chemical modification, we attempted to introduce new disulfide (-SS-) groups into hair using 2-iminothiorane hydrochloride (2-IT). After the evaluation of the setting ability of human hair, the waving permanence (66%) of our proposed permanent hair-setting process clearly improved compared with that of a conventional permanent hair-setting process (48%). Next, it became clear that new -SS- groups were created in the human hair samples as a result of introducing and then oxidizing new -SH groups. This -SS- content in the hair samples was estimated by employing FT-Raman spectroscopy. By examining the Raman bands of the treated land untreated hair, it was seen that each band of treated hair did not change, except for the increase of the -SS- groups. This suggests that hair damage does not occur as a result of the investigated treatment. From these experiments, the chemical modification of keratin fibers using 2-IT was clearly effective for a permanent hair-setting process. (C) 2003 Wiley Periodicals, Inc.