Although surfactants are already used extensively in wool processing as textile auxiliaries, their potential for use in finishing is investigated. The modification of wool fabric properties by the application of surfactants is studied. A recently-developed extraction method makes it possible to distinguish quantitatively between a surfactant adsorbed onto the fiber surface and into the fiber interior. The distribution of a surfactant between the fiber interior and the fiber surface depends on the molecular weight and charge of the surfactant as well as on the temperature and pH of the treatment bath. Under acid conditions (pH 3, 70°C) anionic surfactants are bound almost exclusively inside the fibers; improvements in crease-resistance, stability of fabric thickness and abrasion resistance can be seen. The application of long-chain cationic surfactants at neutral pH values results in marked changes in the fabric properties, even at low concentrations. This is caused by the surfactant being bound to the fiber surface. Although such surfactants can be used successfully on cotton fabrics in soft rinses they lead to increased stiffness when used on wool. This paper was presented at the 8th joint conference (1981) of the Aachen Textile Research Institutes. -- AATA