An isoelectric focusing method followed by silver staining has been developed for the study of keratins which is as effective as two-dimensional electrophoresis and fluorography for hair species identification. Hair from dogs, rabbits, horses, cows, guinea-pigs, donkeys, sheep and cats were successfully identified. Narrow pH ranges were used to observe heterogeneity in human hair. Although this heterogeneity may be affected by environmental conditions, it may be of use in criminalistics.