The phen- otypes demonstrated with this procedure has been correlated with the sodium dodecyl sulfate- polyacrylamide gel electrophoresis (SDS-PAGE) patterns described by other authors. The method described can be applied in the forensic science analysis of a single human hair. Using the same IEF technique we have studied the changes in electrophoretic patterns of cosmet- ically treated hair. The characteristics of the modifications observed and its utility in forensic science work are also discussed in this paper.