An anionic surface-active agent derived from wool proteins was developed as an alternative to the anionic surfactants extensively used in shampoo formulations. The physicochemical properties of this new surface-active agent prepared form wool proteins and its application for human hair treatments were studied. This new product could be considered a new mild anionic surface-active agent, as evidenced by the results found by the evaluation of its physicochemical properties. The new wool anionic surface-active agent was shown to be very substantive to hair, coating the fiber surface, giving rise to a significant improvement in the mechanical properties of the hair fibers, and providing a certain damage-prevention effect on the hair. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 1461-1467, 2010